Flashcards
Waves: reflection, refraction and diffraction
Cards in this deck (5)
- 1Nature of waves Rarefaction: A region where waves move further apart from each other. The wave length increases. Compression: A region where waves move closer together. The wave length decreases. Transverse: Waves that move at a right angle to the vibration. Longitudinal: Waves that move along in the same direction as the vibration. Amplitude: The height of the wave (The loudness) Frequency: The number of waves each second (pitch) Wavelength: The distance between the top of one wave and the top of the next.Waves transfer energy from one place to another with no net movement of matter. In a transverse wave the particles vibrate up and down or side to side. In a longitudinal wave the particles vibrate forwards and backwards (parallel to the direction of the wave).
wave speed = frequency times by wave length
frequency = wave speed divided by wave length
wave length = wave speed divided by frequency - 2Reflection A mirror has a smooth surface so the parallel rays are reflected as parallel rays. This is called regular reflection. Paper is not smooth so the parallel rays are reflected in different directions. This is called diffuse reflection. The angle of incidence the light is reflected at should be the same number as the angle of reflection.Total internal reflection:
As light enters glass it slows down because air and glass have different densities. If the light enters at an angle other than 90 degrees, the light will change direction. If the angle of incidence is greater than the critical angle then the light will be totally internally reflected. - 3Refraction: when light enters a glass block at a angle other than 90 degrees the wave speed slows down causing the light ray to bend towards the normal due to entering a more dense medium. The wave speeds up and bends away from the normal as it leaves the block due to it entering a less dense medium. However if light enters a glass block on the normal (90 degrees) the wave still slows down but does not bend.Light changes direction when it enters a denser substance at an angle because the part of the wave that enters first slows down causing a bend.
- 4Diffraction: The smaller the gap the more they bend , the bigger the gap the less they bend. When waves pass through a gap they diffract. This means they spread out, changing shape as they pass through the gap. Maximum diffraction is when the gap size is equal to the wave length of the wave. If the gap is much smaller than the wave length the waves cannot pass through the gap at all. If the gap is much larger than the wavelength only the edges of the wave bends.Sound is a noise that is made due to the vibrations of particles. Sound waves is a longitudinal wave and they are examples of mechanical waves, they are disturbances that pass through a medium.
Frequency is measured in Hz. Humans can hear between 20-20,000 Hz whereas bats can hear up to 100KHz. - 5An echo is when sound bounces off an object so we then can hear the sound over and over. But the sound decreases in amplitude (loudness) every time it bounces off the wall so every time we hear it again.The Doppler effect:
When an object emits sound or light waves , the waves are emitted in a uniform motion. When a moving source emits sound, because it is moving very fast people appear to hear a high pitch sound when the source first passes but when it moves further away the sound is low pitch. This is because the waves in front get squashed together causing a high frequency and the waves at the back of the source spread out causing a low frequency.
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- Flashcards on Untitled, created by cjgoddard2 on 21/10/2015.
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