Wavelength and Doppler Shift

Question 1

How does light travel?

Answer 1

In waves.

Question 2

What are waves?

Answer 2

Vibrations that transfer energy from place to place without matter being transferred.

Question 3

What is matter?

Answer 3

Solids, liquids and gases.

Question 4

What is the medium?

Answer 4

The substance that allows waves to travel through it. It can be a solid, liquid or a gas.

Question 5

Name two waves that require a medium to travel.

Answer 5

Sound waves and Seismic waves

Question 6

What are transverse waves?

Answer 6

When oscillations are at right angles to the direction of travel and energy transfer.

Question 7

What are longitudinal waves?

Answer 7

When the oscillations are along the same direction as the direction of travel and energy transfer.

Question 8

Give an example of a transverse wave.

Answer 8

Light waves.

Question 9

Give an example of a longitudinal wave.

Answer 9

Sound waves.

Question 10

What is the amplitude of a wave?

Answer 10

It’s maximum disturbance between it’s undisturbed position. This is not the distance between the top and bottom of the wave.

Question 11

What is the wavelength of a wave?

Answer 11

The distance between one point on wave and the same point on the next.

Question 12

What is the frequency of a wave?

Answer 12

The number of waves produced by a source each second. It is also the number that pass a certain point each second.

Question 13

What is frequency measured in?

Answer 13

Hz, Hertz.

Question 14

What is the equation for calculating the speed of a wave?

Answer 14

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.

Question 15

What is the effect of refraction?

Answer 15

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.

Question 16

When does refraction not happen?

Answer 16

When waves cross the boundary at 90 degrees.

Question 17

What is diffraction?

Answer 17

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.

Question 18

When does significant diffraction happen?

Answer 18

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.

Question 19

What is the law of reflection?

Answer 19

The angle of incidence equals the angle of reflection.

Question 20

What is the normal?

Answer 20

A line drawn at the right angle of the reflector.

Question 21

What is the angle of reflection?

Answer 21

It between the reflected ray and the normal.

Question 22

What is the angle of incidence?

Answer 22

Between the incidence (incoming) ray and the normal.

Question 23

What is the image in a plane mirror?

Answer 23

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).

Question 24

What are echoes?

Answer 24

Reflections of sound.

Question 25

What happens when and object or substance vibrates?

Answer 25

It produces sound.
The greater the amplitude, the louder the sound.
The greater the frequency, the higher the pitch.

Question 26

What is the normal range of human hearing?

Answer 26

Between about 20 Hz and 20 kHz, but the range becomes less as we get older.

Question 27

What is sound called that goes above the normal range of human hearing?

Answer 27

Ultrasound.