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  1. 1GCSE Physics B OCR Gateway ² √Physics 5: Space for Reflection
  2. 2What is a satellite?A satellite is an object that orbits a planet in space.
  3. 3Give an example of a natural satellite.Natural satellite - Moon.
  4. 4Give an example of an artificial satellite.Artificial satellite - Communication; Weather; Military satellite.
  5. 5What is gravity?Gravity is a universal force of attraction between masses, i.e. gravitational force.
  6. 6What is the centripetal force provided by for a satellite or planet?It provides the centripetal force needed to keep a satellite in orbit around a planet (e.g. the Moon orbiting the Earth), or a planet in orbit around a star (e.g. the planets orbiting the Sun).
  7. 7Define centripetal force.Centripetal force is the external force acting towards the centre of a circle required to make an object follow a circular path at a constant speed.
  8. 8What does the weight of an object depend on?The weight of an object depends on the gravitational force on the surface of the planet.
  9. 9Give the formula to calculate weight.Weight (N)
    = Mass (kg) x Gravitational field strength (N/kg)
    W
    = m x g
  10. 10What is gravitational field strength on Earth?On Earth, gravitational field strength, g = 10N/kg.
  11. 11How is the gravitational force between two objects affected if the objects are moved further apart?The gravitational force between two objects gets weaker as the objects are moved further apart.
  12. 12How is the force affected if the distance is doubled?If the distance is doubled, the force drops to 1/4.
  13. 13Define inverse square law.The inverse square law is a law stating that the intensity of an effect such as illumination or gravitational force changes in inverse proportion to the square of the distance from the source. (As shown in previous flashcard.)
  14. 14How are the planets affected if there is a difference in gravitational force?The difference in gravitational force means that:
    - planets closer to the Sun travel very quickly and have short orbital periods.
    - planets further from the Sun travel very slowly and have long orbital periods.
  15. 15What does the orbital period of a planet depend on?The orbital period of a planet depends upon its distance from the Sun.
  16. 16Do planets very close to the Sun experience a high gravitational force or a low gravitational force compared to planets that are further away?Planets very close to the Sun experience a high gravitational force compared to planets that are further away.
  17. 17Compare the orbit of a periodic comet and a planet.A periodic comet has a highly elliptical orbit (oval-shaped, rather than circular) around the Sun, unlike the planets, which have highlt-circular orbits.
  18. 18What happens to the speed of a comet as it travels past the Sun?When a comet is close to the Sun it has to travel very fast to escape the gravitational force (tail away from Sun). When the comet is further away from the Sun, it travels more slowly because the Sun's gravity pulls it back (tail towards Sun).
  19. 19What is the effect of a comet travelling around the Sun similar to?The effect of a comet travelling around the Sun is similar to a ball being thrown up into the air: it slows down as it gets higher and speeds up as it gets closer to the Earth.
  20. 20Is it natural or artificial satellites that can orbit at different heights above the Earth's surface?Artificial satellites can orbit at different heights above the Earth's surface.
  21. 21How is a satellite's orbital period affected by height?A satellite's orbital period (the time it takes to make one complete orbit) increases with height above the Earth.
  22. 22How is a satellite's use determined?The height at which a satellite orbits, and its period, determines what it can be used for.
  23. 23Give two ways in which to determine a satellite in low polar orbit.Two ways in which to determine a satellite in low polar orbit include:
    - travel very quickly
    - go around the Earth several time each day.
  24. 24Give three uses of a satellite in low polar orbit.Three uses of a satellite in low polar orbit include:
    - imaging the Earth' surface
    - weather forecasting
    - military uses.
  25. 25Give three ways in which to determine a geostationary satellite.Three ways in which to determine a geostationary satellite include:
    - orbit much higher above the Earth
    - take 24 hours to complete one orbit
    - remain above a fixed position on the Earth's equator.
  26. 26Give two uses of a geostationary satellite.Two uses of a geostationary satellite include:
    - communications, for example, satellite television
    - weather forecasting.
  27. 27Why does a satellite travel in a circular orbit?A satellite would naturally travel in a straight line. However, Earth's gravitational force causes it to continually accelerate towards Earth, and prevents it from flying off at a tangent. The two effects balance, causing the satellite to remain in a circular orbit.
  28. 28Why must the forward speed, or tangential motion, of a satellite must be just right to keep the satellite in orbit?The forward speed, or tangential motion, of a satellite must be just right to keep the satellite in orbit:
    - if the tangential motion is too slow, the satellite will fall to Earth
    - if the tangential motion is too fast, the satellite will travel away into space.
  29. 29Why do artificial satellites in low polar orbits travel faster than those in higher orbits?Artificial satellites in low polar orbits feel a strong gravitational force dragging them towards the Earth, so they travel faster than those in high orbits.
  30. 30How does the position of a satellite in low polar orbit affect its movement?A satellite in low polar orbit is close to the ground, so the gravitational attraction is strong. This produces a high centripetal acceleration, so the tangential speed must be high to keep the gravitational force balanced and the satellite moving in a circle.
  31. 31How does the position of a geostationary satellite affect its movement?A geostationary satellite is further from the ground, so the gravitational attraction is weaker. This produces a lower centripetal acceleration, so the tangential speed must be less to keep the gravitational force balanced and the satellite moving in a circle.
    N.B. Geostationary satellites move more slowly and have further to travel.
  32. 32What can satellites also be used for?Satellites can also be used for scientific research and global positioning systems (GPS).
  33. 33What is a scalar quantity?A scalar quantity is a quantity in which direction is not important. All that matters is its magnitude (its size).
  34. 34List four examples of scalar quantities.For example, these quantities are scalar:
    - mass
    - energy
    - speed
    - time.
  35. 35What is a vector quantity?A vector quantity is a quantity in which direction and magnitude (its size) is important.
  36. 36List three examples of vector quantities.For example, these quantities are vector:
    - force
    - acceleration
    - velocity.
  37. 37What do equations of motion link together?Equations of motion link together distance travelled, initial and final velocities, acceleration and time.
  38. 38What is speed?Speed is a scalar quantity – it is the rate of change in the distance travelled by an object in a particular time.
  39. 39Why do you need to calculate the average speed for a journey made by an object?You need to calculate the average speed as the speed of an object can change during the course of its journey.
  40. 40Give the formula to calculate the average speed for a journey.Average speed
    = Total distance / Total time taken
  41. 41Define relative speed.Relative speed is the speed of an object, relative to another object that is being treated to be at rest.
  42. 42Give a situation where relative speed is used in terms to describe motion.If two objects are moving near to each, their motion is described in terms of their relative speed.
  43. 43Is direction important or non-important when considering motion?Direction is important when considering motion.
  44. 44If two cars are travelling on a straight road in which direction will their relative speed be higher?Two cars are travelling on a straight road will have a higher relative speed if they are moving towards each other than if they are travelling in the same direction.
  45. 45If two objects are travelling towards each other, how is their motion described, in terms of relative speed?Example 1
    Car A and Car B are travelling towards each other on a straight road. Each car is travelling at 10m/s. The relative speed of Car A and Car B is 20m/s. That is, if you're in Car A, it will look like Car B is travelling towards you at a speed of 20m/s.
  46. 46If two objects are travelling in the same direction, how is their motion described, in terms of relative speed?Example 2
    Car C and Car D are travelling in the same direction on a straight road. Car D is travelling at 8m/s and Car C is travelling at 10m/s. Every second, Car C will get 2m closer to Car D, which means that Car C's relative speed is 2m/s.
  47. 47Define velocity.Velocity is an object's rate of displacement (change of distance) or speed in a particular direction
  48. 48Give the formula to calculate velocity and displacement.v = u + at
    s = (u + v / 2) x t
    where:
    u = initial velocity,
    v = final velocity,
    a = acceleration,
    t = time,
    s = displacement.
  49. 49Example A bike travelling at 5m/s accelerates at 3m/s² for 5 seconds. a) What is the bike's final velocity? b) How far did the bike travel whilst accelerating?Example
    a) v = u + at
    v = 5 + (3 x 5)
    = 20m/s
    b) s = (u + v / 2) x t
    s = (5 + 20 / 2) x 5
    = 62.5m
  50. 50Give the formula to calculate an object's final velocity, displacement, acceleration, or the time it was travelling.v² = u² + 2as
    s = ut + 1/2 at²
  51. 51Example 1 A runner starts a race and accelerates at 2.5m/s² for the first 20m of the race. What is the runner's final velocity?Example 1
    v² = u² + 2as
    v² = 0² + (2 x 2.5 x 20) = 100
    v = √100
    = 10m/s
  52. 52Example 2 A car travelling at 20m/s accelerates at 3m/s² for 20 seconds. How far has the car travelled in this time?Example 2
    s = ut + 1/2at²
    s = (20 x 20) + (1/2 x 3 x 20²)
    s = 400 + 600
    = 1000m
  53. 53If two forces or velocities are parallel, how is it possible to calculate their total effect?If two forces or velocities are parallel, it is possible to calculate their total effect from a vector diagram:
    - Parallel vectors in the same direction add up:
    Fᴿ = F1 + F2
    - Parallel vectors in opposite directions subtract:
    Fᴿ = F1 - F2
  54. 54How can you work out the resultant force/velocity if two forces or velocities are acting at right angles on the same object?If two forces or velocities are acting at right angles on the same object, you can work out the resultant force/velocity by using Pythagoras' theorem:
    Fᴿ = √F1² + F2²
  55. 55What are projectiles?When objects such as balls or darts move through Earth's gravitational field (or more commonly, the air) they are called projectiles.
  56. 56Give examples of objects which are projectiles when moving through the air.When moving through the air, the following are all examples of projectiles:
    - Golf balls
    - Footballs
    - Netballs
    - Darts
    - Long-jumpers.
  57. 57What is the path that a projectile follows known as?The path that a projectile follows is known as its trajectory.
  58. 58If a projectile is launched horizontally on Earth, and there is no air resistance acting on it, what will the projectile have?If a projectile is launched horizontally on Earth, and there is no air resistance acting on it, the projectile will have:
    - a constant horizontal velocity
    - a steadily increasing vertical velocity.
  59. 59What are the horizontal and vertical velocities?The horizontal and vertical velocities are vectors.
  60. 60If air resistance is ignored, what will the only force acting on the projectile be?If air resistance is ignored, the only force acting on the projectile is gravity.
  61. 61How does Earth's gravitational field affect the projectile?The Earth's gravitational field causes the projectile to accelerate towards the ground, so it only affects the projectile's vertical velocity.
  62. 62What is a parabolic trajectory?Because of the pull of gravity, objects projected horizontally on Earth follow a downward curving path, known as a parabolic trajectory.
  63. 63What does the horizontal range depend on only?The horizontal range depends only on the launch angle (measured from the horizontal).
  64. 64At which degree will footballs travel the greatest distance when launched?Footballs launched at 45° will travel the greatest distance.
  65. 65How can the horizontal and vertical velocities of a projectile be treated (as vectors)?The horizontal and vertical velocities of a projectile can be treated as separate vectors.
  66. 66What is a projectile's resultant velocity?A projectile's resultant velocity is the vector sum of the horizontal and vertical velocities:
    Vᴿ = √V1² + V2²
  67. 67Why does a projectile have no acceleration in the horizontal direction?A projectile has no acceleration in the horizontal direction. This is because gravity only affects its vertical velocity.
  68. 68Which equations can be used for objects that are projected horizontally above the Earth, where gravity is uniform?You can use the velocity and displacement equations for objects that are projected horizontally above the Earth, where gravity is uniform.
  69. 69Example A stone is kicked off a cliff with a horizontal velocity of 3m/s. After 3 seconds, it lands in the sea 45m below. a) What is the magnitude (size) of the resultant velocity of the stone when it hits the sea? b) What is the vector sum of the two velocities?a) Horizontally, the stone's velocity doesn't change.
    Vertically, the stone's velocity increases from its initial velocity of 0m/s, due to gravity.
    (Remember that acceleration due to gravity is 10m/s².)
    v = u + at = 0 + (10 x 3)
    = 30m/s vertically
    b) v² = 3² + 30²
    v = √909
    = 30.1m/s
  70. 70What does Newton's Third Law of Motion state?Newton's Third Law of Motion states that every action has an equal and opposite reaction, i.e. when an object collides with another, or two bodies interact, they exert equal and opposite forces on each other.
  71. 71Give an example of Newton's Third Law of Motion in practice.For example, when you stand on solid ground:
    - you exert a force on the ground (your weight)
    - the ground exerts an equal and opposite force on you (contact force).
    Gravity pulls you down towards the Earth and you are pulling the Earth towards you.
  72. 72Give the formula to calculate momentum.Momentum = Mass x Velocity
  73. 73How will an increase in an object's mass and/or velocity?An increase in an object's mass and/or velocity will also increase its momentum.
  74. 74Example Calculate the momentum of a person of mass 60kg travelling at 0.5m/s.Momentum = Mass x Velocity
    = 60 x 0.5
    = 30kgm/s
  75. 75In a collision, in which direction are the velocities of the objects colliding?In a collision, the velocities of the objects colliding are parallel.
  76. 76What happens to Object A if Object A hits Object B with a force?If Object A hits Object B with a force, then Object A will be hit by Object B with an equal force.
  77. 77Give two examples of where this theory (Object A hits Object B with a force, Object A is hit with an equal force by Object B) is put into practice.For example:
    - if a lorry crashes into a car, then the car hits the lorry with the same force
    - if a ball is hit with a racket, then the racket feels the same force from the ball and recoils.
  78. 78What is acceleration?Acceleration is the rate of change of an object's velocity over time.
  79. 79What are many injuries in vehicle collisions, and sporting injuries caused by?Many injuries in vehicle collisions, and sporting injuries, are caused by rapid acceleration (usually a sudden slowing down) of the body.
  80. 80How do safety features in vehicles reduce injury?Safety features in vehicles reduce injury by spreading out the acceleration over a greater period of time.
  81. 81How do safety features in a vehicle affect a passenger's momentum?Safety features in a vehicle cause a passenger's momentum to be reduced more slowly.
  82. 82Give the formula to calculate force, change in momentum, and time taken.Force (N) = Change in momentum / Time
  83. 83Example A boy of mass 50kg is walking at 2m/s (v¹). A gust of wind blows the boy forward for 2 seconds and he ends up running at 5m/s (v²). What is the force of the wind?Force = Change in momentum / Time
    = mv² -mv¹ / t
    = (50 x 5) - (50 x 2) / 2
    = 250 - 100 / 2
    = 75N
  84. 84What does spreading a change in momentum over a longer time reduce?Spreading a change in momentum over a longer time reduces:
    - the forces required to act
    - injuries caused by the forces.
  85. 85Define momentum.Momentum is a quantity relating to a moving object that is calculated by multiplying its mass by its velocity.
  86. 86Is the total momentum (of a system) before a collision different or the same as the total momentum afterwards?The total momentum (of a system) before a collision is the same as the total momentum afterwards.
  87. 87Give four examples and descriptions of conservation of momentum.Example of Conservation of Momentum:
    Recoil
    Description:
    The total momentum of a gun and bullet is zero. If the bullet is then fired, the total momentum is still zero. The bullet moves faster than the gun but it has a smaller mass, so their momenta are equal but acting in opposite directions, thus cancelling each other out.
    Example of Conservation of Momentum:
    Explosion
    Description:
    Before an explosion, the total momentum is zero. After an explosion, each fragment flies off in a different direction. The momentum of one fragment will cancel out the momentum of another fragment that's travelling in the opposite direction at the same momentum.
    Example of Conservation of Momentum:
    Rocket Propulsion
    Description:
    When a rocket's engines fire in space, the rocket speed up, but the total momentum of the system is conserved. This is because the forward momentum of the rocket is cancelled out by the backward momentum of the gas it fires out.
    Example of Conservation of Momentum:
    Collision
    Description:
    During a collision momentum is conserved. If two objects join (coalesce) during the collision, the momentum after the collision must equal the sum of their individual momentums.
    m¹ u¹ + m² u² = (m¹ + m²) v
    (where u and v are initial and final velocities/speeds)
  88. 88Describe the motion of gas particles.The particles in a gas are in constant motion, moving quickly and randomly in any direction.
  89. 89What happens as particles collide with walls of their container?As particles collide with the walls of their container they exert a force on the wall.
  90. 90What is pressure?Pressure is force per unit area.
  91. 91How is the pressure of gas particles increased in a container?For a given area of a container wall, the greater the force exerted, the greater the number of collisions between the particles and the wall, the greater the gas pressure.
  92. 92Which three things are affected if the gas particles are squashed into a smaller volume?If the gas particles are squashed into a smaller volume:
    - the same number of particles will have less space to move in
    - each particle will collide with the walls more frequently
    - the pressure inside the container increases.
  93. 93Which four things are affected if the temperature of the gas is increased?If the temperature of the gas is increased:
    - the particles gain energy
    - with increased kinetic energy, the particles move more quickly
    - each particle will collide with the wall more frequently and collide with more force
    - the pressure inside the container increases.
  94. 94What does a particle undergo, as it strikes the wall of its container?As a particle strikes the wall of its container, it undergoes a change in its momentum.
  95. 95What does the particle's change of momentum produce on the wall?The particle's change in momentum produces a force on the wall.
  96. 96What does the size of the force depend upon?The size of the force depends upon the length of time that the particle is in contact with the wall (time taken).
    Force = Change in momentum / Time taken
  97. 97At launch, what does a rocket require to enable it to accelerate?At launch, a rocket requires a large force to enable it to accelerate.
  98. 98What is this force provided by?This force is provided by the exhaust gases.
  99. 99Show how Newton's Third Law of Motion can be used to explain how the rocket is propelled into space.The force pushing the gas backwards out of the rocket's exhaust equals the forward force of the gas on the rocket.
  100. 100How is a force on the rocket produced?The fast-moving particles in the gas collide with the walls of the rocket. This produces a force on the rocket.
  101. 101What do rockets used to launch satellites into orbit require?Rockets used to launch satellites into orbit require very large forces to lift both the rocket and the satellite.
  102. 102How is sufficient force achieved (by a rocket with satellite)?Sufficient force is achieved (by a rocket with satellite) by:
    - a large number of particles of exhaust gas
    - the particles moving at high speed.
  103. 103Do radio waves have a very long or very short wavelength?Radio waves have a very long wavelength (1m - 10km).
  104. 104How are different frequencies of radio waves affected by the Earth's atmosphere?Different frequencies of radio waves are affected by the Earth's atmosphere in different ways:
    1) Some frequencies (between 30MHz and 30GHz) pass through the Earth's atmosphere (relatively short wavelength).
    2) Some frequencies (above 30GHz) are reduced in strength, or even stopped, by the Earth's atmosphere. They are absorbed and scattered by rain, dust and other atmospheric effects.
    3) Some frequencies (below 30MHz) are reflected by a part of the Earth's upper atmosphere called the ionosphere.
  105. 105Why can't the same frequencies be used to send information to all types of satellite?The same frequencies can't be used to send information to all types of satellite for the following reasons. Low orbiting satellites use low frequency signals. Geostationary satellites are much further above the Earth so they need to use high frequency signals.
  106. 106Why are microwaves, instead of radio waves, used to transmit information to orbiting artificial satellites, which then retransmit information back to Earth?Microwaves are used to transmit information to orbiting artificial satellites, which then retransmit information back to Earth. This is because microwaves have a higher frequency, and shorter wavelength, than radio waves.
  107. 107When a wave meets an obstacle, such as a hill, how does it react?When a wave meets an obstacle, such as a hill, it reacts by spreading around the hill.
  108. 108If a wave meets a gap and spreads out through the gap, what can the wave be described as?If a wave meets a gap and spreads out through it, it causes the wave to be described as diffracted, i.e. spread out from the edges.
  109. 109How do different sized gaps affect diffraction?Different sized gaps cause different amounts of diffraction.
  110. 110Give an example of different sized gaps causing different amounts of diffraction.For example, if you stand in a room with the door open, you can hear sounds from outside the room. This is because the wavelength of sound is about the same size of the doorway, so the sound waves spread out as they come through the door.
  111. 111What does the amount a wave is diffracted depend on?The amount a wave is diffracted depends on the size of gap and the wavelength of the wave:
    - Large gaps allow waves to pass straight through without diffracting.
    - Diffraction is most obvious when the size of the gap is equal to the wavelength.
  112. 112What are the two features of light that make it an electromagnetic wave?Light, as an electromagnetic wave, is a transverse wave and travels in straight lines.
  113. 113What does light being a transverse wave and travelling in straight lines result in?As a result, you see sharp-edged shadows and a solar eclipse when the Moon passes between the Sun and the Earth.
  114. 114What can make light look as though it bends?Diffraction and refraction can make light look as though it bends.
  115. 115What happens to waves of light when light is diffracted?When light is diffracted, the diffracted waves behave like separate beams of light, and can overlap one another.
  116. 116What is caused when two waves overlap?When two waves overlap, it causes interference.
  117. 117What does interference produce areas of?Interference produces areas of:
    - reinforcement (where waves add together)
    - cancellation (where waves subtract from each other).
  118. 118Give an example where areas of reinforcement and cancellation result from water waves overlapping.For example, when water waves overlap:
    - areas of reinforcement are where the ripples are deeper, because their height is made up of two ripples added together.
    - areas of cancellation are where the water's surface is flat, because the peak of one wave fills in the trough of the other.
  119. 119Give an example of the effects of reinforcement and cancellation on sound waves and light waves.Sound Waves -
    Effect of Reinforcement:
    Loud areas
    Effect of Cancellation:
    Quiet areas
    Light waves-
    Effect of Reinforcement:
    Bright areas
    Effect of Cancellation:
    Dark areas.
  120. 120When only is a stable interference pattern produced?A stable interference pattern is only produced when the wave sources are coherent (have the same frequency).
  121. 121If a stable interference pattern is produced when the wave sources are coherent, what does this make the light sources?If a stable interference pattern is produced when the wave sources are coherent, the light sources are monochromatic.
  122. 122What are interference patterns evidence for?Interference patterns are evidence for the wave nature of light.
  123. 123What three features do coherent wave sources have?Coherent wave sources:
    - have the same frequency
    - are in phase
    - have the same amplitude.
  124. 124When does constructive interference (reinforcement) occur?Constructive interference (reinforcement) occurs when identical waves arrive in phase at a point. This produces a wave with larger amplitude, so you see bright fringes.
  125. 125When does destructive interference (cancellation) occur?Destructive interference (cancellation) occurs when identical waves arrive out of phase. The amplitude of the resulting wave is zero, so you see dark fringes.
  126. 126What results by replacing the double slit, through which the light is shone, with a single slit?Replacing the double slit, through which the light is shone, with a single slit results in a pattern with a much brighter central fringe.
    N.B. Slit must be about the same width as the wavelength of light.
  127. 127What is a medium?A medium is a substance that waves can travel through.
  128. 128What is a line at 90° to the surface of a medium known as?A line at 90° to the surface of a medium is known as the normal.
  129. 129What is refraction?Refraction is when light travels from one medium to another at an angle to the normal it changes direction.
  130. 130Where does refraction occur?Refraction occurs at the boundary between two media.
  131. 131Why does refraction occur at the boundary between two media?Refraction occurs at the boundary between two media due to a change in the wave speed as it travels through the different densities.
  132. 132What is the angle of refraction, r?The angle at which the light ray travels through the second medium is the angle of refraction, r.
  133. 133What does the angle of refraction, r, depend on?The angle of refraction, r, depends on the angle at which the light hits the boundary between the media, that is, the angle of incidence, i.
  134. 134How is the wave affected if light travels into a more dense medium (from air into glass)?As light travels into a more dense medium (from air into glass), the wave speed decreases. The wave 'bends' towards the normal. The angle of refraction, r, is smaller than the angle of incidence, i.
  135. 135How is the wave affected if light travels into a less dense medium (from glass into air)?As light travels into a less dense medium (from glass into air), it bends away from the normal as it speeds up. The angle of refraction, r, is bigger than the angle of incidence, i.
  136. 136What is the refractive index of a medium?The refractive index of a medium is a measure of how much the medium refracts light rays as they cross its boundary.
  137. 137If a material has a higher refractive index what is the degree of bending produced?A material with a higher refractive index produces a greater degree of bending.
  138. 138When does the amount of refraction increase in reference to wave speed?The amount of refraction increases when there's a greater change in light's wave speed as it passes from one medium to another.
  139. 139Give the formula to calculate the refractive index, n, by comparing the speed of light in the medium with the fastest speed that light can travel (i.e. in a vacuum).Refractive index, n = Speed of light in a vacuum / Speed of light in a medium
  140. 140If materials have higher refractive indices how does are their critical angles affected?Materials with higher refractive indices have a smaller critical angle.
  141. 141Give an example of three materials, their refractive indexes and their critical angles.Material:
    Water
    Refractive Index:
    1.33
    Critical Angle
    48.8°
    Material:
    Glass
    Refractive Index:
    1.50
    Critical Angle:
    41.8°
    Material:
    Diamond
    Refractive Index:
    2.42
    Critical Angle:
    24.4°
  142. 142Does diamond have a high or low refractive index?Diamond has a high refractive index.
  143. 143What will all light incident on the diamond-air boundary at an angle greater than 24.4 degrees undergo?All light incident on the diamond-air boundary at an angle greater than 24.4 degrees will undergo total internal reflection (TIR).
  144. 144What does this total internal reflection of all light incident on a diamond-air boundary produce?This total internal reflection of all light incident on a diamond-air boundary produces the sparkling effect of diamonds.
  145. 145What is the critical angle?The critical angle is the maximum angle of incidence (measured form the normal) before total internal reflection (TIR) occurs.
  146. 146Do different media have different or similar critical angles?Different media have different critical angles.
  147. 147Why isn't all light refracted when it leaves glass or water to travel through air?Not all light is refracted when it leaves glass or water to travel through air as some of the light is reflected from the surface:
    1) If the angle of incidence is less than the critical angle, most of the light is refracted into the air.
    2) If light hits the boundary at exactly the critical angle, it undergoes maximum refraction, emerging at 90° to the normal.
    3) If the angle of incidence is larger than the critical angle, no light is refracted, i.e. all the light is reflected back into the medium. This is known as total internal reflection.
  148. 148What does total internal reflection rely on?Total internal reflection relies on light being refracted away from the normal as the light ray speeds up.
  149. 149When does total internal reflection only occur?Total internal reflection only occurs when:
    - light travels from a medium with a high refractive index into a medium with a lower refractive index
    - the angle of incidence is more than the critical angle.
  150. 150How does the height of a medium's refractive index affect the critical angle?The higher a medium's refractive index, the lower the critical angle.
  151. 151Give the formula to calculate the critical angle, c.sin c = nr / ni
    where :
    nr = refractive index of air
    ni = refractive index of medium
  152. 152List some uses of total internal reflection.Uses of total internal reflection include optical fibres and bike reflectors.
  153. 153When is light incident on the glass-air boundary totally internally reflected?Light incident on the glass-air boundary at an angle greater than the critical angle is totally internally reflected (TIR).
  154. 154How does light travel down the length of a fibre optic cable?Light travels down the length of a fibre optic cable by total internal reflection.
  155. 155What are fibre optics used for?Fibre optics are used:
    - to send digital signals for communication
    - in endoscopes to observe tissues inside the body.
  156. 156In bike reflectors, how does light undergo total internal reflection?In bike reflectors, total internal reflection occurs at the plastic-air boundary and leaves the reflector parallel to the ray of light entering.
  157. 157What is light made up?Light is made up of the colours of the spectrum.
  158. 158What do all the colours travel at the same speed in?All the colours travel at the same speed in a vacuum.
  159. 159What do all the colours travel at different speeds in?All the colours travel at different speeds in other media.
  160. 160How is light affected when it travels through a prism?When light travels through a prism it is slowed down, and therefore refracted.
  161. 161Which colours diffract by different amounts?Different colours diffract by different amounts:
    - Blue/violet light is slowed down the most.
    - Red light s slowed down the least.
  162. 162If blue light is slowed down the most, what does this say about its direction?This means that as blue light is slowed down the most it is deviated (changes direction) more than red light. This is dispersion.
  163. 163Why are the spectral colours slowed down by different amounts when they travel through a prism?The spectral colours are slowed down by different amounts when they travel through a prism because they have different wavelengths.
  164. 164Are the colours with shorter or longer wavelengths slowed and deviated more than the colours with longer or shorter wavelengths?The colours with shorter wavelengths are slowed and deviated more than the colours that have longer wavelengths.
  165. 165What does this mean about glass's refractive index for the colours that have shorter wavelengths?This means that glass has a higher refractive index for the colours that have shorter wavelengths.
  166. 166Does blue light have a greater or lesser refractive index than red light?Blue light has a greater refractive index than red light.

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Karteikarten am Ohne Titel, erstellt von cecily.edwards1 am 08/04/2014.
Erstellt von
cecily.edwards1 · Apr 2014
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16 Nov 2016
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