Wavelength and Doppler Shift Flashcards
How does light travel?
In waves.
What are waves?
Vibrations that transfer energy from place to place without matter being transferred.
What is matter?
Solids, liquids and gases.
What is the medium?
The substance that allows waves to travel through it. It can be a solid, liquid or a gas.
Name two waves that require a medium to travel.
Sound waves and Seismic waves
What are transverse waves?
When oscillations are at right angles to the direction of travel and energy transfer.
What are longitudinal waves?
When the oscillations are along the same direction as the direction of travel and energy transfer.
Give an example of a transverse wave.
Light waves.
Give an example of a longitudinal wave.
Sound waves.
What is the amplitude of a wave?
It’s maximum disturbance between it’s undisturbed position. This is not the distance between the top and bottom of the wave.
What is the wavelength of a wave?
The distance between one point on wave and the same point on the next.
What is the frequency of a wave?
The number of waves produced by a source each second. It is also the number that pass a certain point each second.
What is frequency measured in?
Hz, Hertz.
What is the equation for calculating the speed of a wave?
v = f × λ
v is the wave speed in metres per second, m/s
f is the frequency in hertz, Hz
λ (lambda) is the wavelength in metres, m.
What is the effect of refraction?
Sound waves and light waves change speed when they pass across the boundary between two substances with different densities, such as air and glass. This causes them to change direction.
When does refraction not happen?
When waves cross the boundary at 90 degrees.
What is diffraction?
When waves meet a gap in a barrier, they carry on through the gap. However, the waves spread out to some extent into the area beyond the gap.
When does significant diffraction happen?
Significant diffraction only happens when the wavelength is of the same order of magnitude as the gap. For example:
a gap similar to the wavelength causes a lot of spreading with no sharp shadow, e.g. sound through a doorway
a gap much larger than the wavelength causes little spreading and a sharp shadow, e.g. light through a doorway.
What is the law of reflection?
The angle of incidence equals the angle of reflection.
What is the normal?
A line drawn at the right angle of the reflector.
What is the angle of reflection?
It between the reflected ray and the normal.
What is the angle of incidence?
Between the incidence (incoming) ray and the normal.
What is the image in a plane mirror?
Virtual (it cannot be touched or projected onto a screen).
Upright (if you stand in front of a mirror, you look the right way up).
Laterally inverted (if you stand in front of a mirror, your left side seems to be on the right in the reflection).
What are echoes?
Reflections of sound.
What happens when and object or substance vibrates?
It produces sound.
The greater the amplitude, the louder the sound.
The greater the frequency, the higher the pitch.
What is the normal range of human hearing?
Between about 20 Hz and 20 kHz, but the range becomes less as we get older.
What is sound called that goes above the normal range of human hearing?
Ultrasound.
