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PHYSICS CHAPTER 6- Waves
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- 1What is a longitudinal wave?A wave in which, the vibration are parallel to the direction of energy transfer.
- 2What is echo sounding?When ships use high frequency sound waves to find the depth of the seabed or locate shoals of fish
- 3What happens when a light ray passes through a dnser medium?It refracts TOWARDS the normal
- 4What do the terms 'infra' and 'ultra' mean literally?• Infra- LESS THAN
• Ultra- MORE THAN - 5What happens when all wavelengths of colour are reflected by an object?It appears white
- 6What type of waves are electromagnetic waves?Transverse waves
- 7When is the angle of refraction bigger than the angle of incidence?When the light ray enters a less dense medium
- 8What is the amplitude of a wave?The maximum displacement of a wave from the undisturbed position
- 9Which electromagnetic wave has the highest frequency?Gamma rays
- 10The higher the wavelength, the ......................................... the frequency.Lower
- 11What is a wave front?A line that joins all the points on a wave which are moving up and down together at the same time
- 12Why are microwaves and not radio waves used for satellite communication?Radio waves are refracted in the ionosphere (the upper layers of the atmosphere) whereas the microwaves pass straight through the ionosphere to the satellite.
- 13Give 4 uses of ultraviolet radiation.• Fluorescent lighting
•Sun beds
• Security pens
• Detecting forged bank notes - 14What is a P wave?A primary (pressure) wave. It is longitudinal and similar to a sound wave. The speed increases with depth in the Earth and is slower in liquids than in solids.
- 15What is a transverse wave?A wave in which the vibration are from side to side at right angles to the direction of energy transfer
- 16What are the units for frequency, wave speed and wavelength?• Frequency- Hz
• Wave speed- m/s
• Wavelength- m - 17How does a ripple tank work?An oscillating wooden block is suspended above a shallow tank of water with elastic bands so that it is just touching the surface. A motor is screwed on the wood, that has an off-centre weight attached to the axle. As the axle rotates the motor wobbles, shaking the wood and generating ripples, the patterns appearing on a viewing screen or table.
- 18What are 4 uses of ultrasound scanning?• To check the development of unborn babies by creating images of the fetus
• To measure the speed of blood flow in a vein or artery
• To find cracks or gaps in metal objects such as aircraft structured and oil pipelines
• To measure the thickness of objects - 19State 3 uses of X-rays.• CAT (computer axial tomography) scans
• To produce clear photographs of bones
• Fluoroscopy (moving images of internal structures of patients) - 20How does a radio transmitter work?Radio waves can be produced by oscillations in electrical circuits. When current flows through a wire, an electrical field is created around the wire. When the current changes, the electric field changes to and this changing current produces radio waves.
- 21What is the range of the wavelengths of microwaves?1mm - 30 cm
- 22What colour does a red object appear through a blue filter?Black
- 23What happens when white light is shone through a red filter?All wavelengths except for red are absorbed so red light comes out the other side.
- 24What wavelngths does a white object reflect?All wavelengths
- 25What is the principal focus?The point at which the parallel rays cross over or appear to have come from
- 26Why does the Earth emit infrared radiation?It's temperature is higher than its surroundings
- 27How does microwave radiation cook food?Microwaves penetrate about 1cm of the outer layers of the food before being absorbed. The energy transferred by the microwaves make the water and fat molecules vibrate more, increasing kinetic energy and then the energy is transferred to the centre of the food by conduction.
- 28The shorter the wavelength of an electromagnetic wave, the .............................. dangerous the radiation.More
- 29What is the focal length of a lens?The distance from the centre of the lens to the principal focus
- 30When is a virtual image produced?When an object is placed between the principal focus and a convex lens
- 31Which type of lens brings rays together at the principal focus?Convex lens
- 32What are S waves?A secondary (shear) wave. It is a transverse wave with generally increasing wavelength with the depth of teh Earth, but always less than P waves. Cannot travel through liquids.
- 33What determines the colour of an object?The wavelengths that it reflects- e.g. a blue object absorbs all wavelengths but reflects blue
- 34What is a concave lens?A diverging lens that it narrowest in the middle and widest on the outside
- 35Black surfaces are good ..................................... of radiation.Absorbers
- 36A good absorber of infrared radiation is a ................................ emitter.Good
- 37What is the tpical range of hearing for a human?20Hz to 20kHz
- 38How do ultrasound scans work?Agel is placed on the person's body between the ultrasound probe and the skin. Without this gel nearly all of the ultrasound would be reflected at the skin producing an unclear image. A pulse of ultrasound pass through lots of different materials and the returning echoes are recorded. Reflections from different layers return at different times from different depths. The depth is calculated using speed = distance/ time and the data is used ti build up an image of the different layers.
- 39What is the name of the lens where rays of light passing through cross over?Convex lens
- 40The intensity and peak wavelength of the radiation emitted depend only on the object's ...................................................Temperature
- 41What is the magnification equation?Magnification = Image Height/ Object height
- 42At a given temperature a perfect black body, .......................................... all wavelengths.Radiates
- 43What happens when an object is absorbing infrared radiation faster than it emits?It is cooling down and is cooler than its suroundings
- 44What is thermal equilibrium?When the rates at which radiation is absorbed and at which it is emitted are the same and the temperature of the object does not change
- 45Why do white objects take longer to reach thermal equilibrium than black objects do?White objects reflect infrared radiation whereas black objects absorb them from surroundings
- 46What factors affect the mean temperature of the Earth?• Rates of absorption
• Rates of emission
• Reflection of radiation - 47Why do greenhouse gases keep the Earth warmer?They re-radiated the infrared radiation so the Earth will absorb it and the more greenhouse gases, the more absorption and the rates of absorption will exceed the rates of emission, warming up the Earth.
- 48How do microwaves cook food?Microwaves penetrate about 1 cm into the outer layers of the food before being absorbed. The energy transferred by the waves makes water and fat molecules vibrate more and energy is transferred from these vibration molecules to the centre of the food by conduction.
- 49What is radar?Uses microwaves to detect aircraft outside the normal range of sight and hearing. These microwaves can pass through the atmosphere even, when visible light is blocked by clouds or dust.
- 50How does radar work?Works by sending out microwave pulses from a transmitter mounted on the aircraft. Microwaves reflect from a metal target similar to light reflecting off a mirror. These reflected microwaves are detected by the radar system's receiving antenna. And then s=d/t is used to calculate how far away the target is.
- 51How do radio transmitters work?Radio waves can be produced by oscillations in electrical circuits. When a current flows through a wire, it creates an electric field around the wire. When this current changes the electric field changes as well. This changing current produces radio waves- this is how radio transmitters work.
- 52Why are microwaves and not radio waves used for satellite communication?Because microwaves with shorter wavelengths are not reflected or refracted so can pass straight through the ionosphere. However radio waves are refracted in the ionosphere so returns back to the Earth's surface, therefore cannot reach satellites.
- 53Give 3 uses of microwaves○ Cooking
○ Satellited phones
○ Satellite TV - 54Give 3 uses of radio waves○ satellite transmissions
○ Television
○ Radio - 55What is the order of the electromagnetic spectrum?
- 56How do X-rays produce an image of bones?X-rays pass through soft tissue in the body, but will be absorbed by bone. X-ray images can therefore be used to check for broken bones.
- 57How does a radioactive tracer work?A radioactive tracer is a radioactive isotope that emits gamma rays. A gamma camera is used to monitor where gamma rays are emitted from in the body, to produce a moving image that show how organs are functioning.
- 58What is the key difference between X-rays and gamma rays?How they are produced- gamma rays are emitted from the nucleus of an unstable atom during radioactive decay, whereas X-rays are generated by an X-ray machine when high-speed electrons collide with metals and lose energy.
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- Year 11 Physics Fichas sobre PHYSICS CHAPTER 6- Waves, creado por UnknownSnowFlake 123 el 21/04/2017.
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