Propagation Of Light

Question 1

Continuous waves and wave pulses

Answer 1

Continuous wave- uninterrupted/continuous wave of light.

Wave pulses- pulses of light, such as flashing light with gaps in between

Question 2

Define-

Wavelength

Amplitude

Frequency

Answer 2

Wavelength - distance between two adjacent crest. Measured in nanometers and shown as ‘lambda’ (line giraffe)

Amplitude- distance from centre line troop of crest or bottom of trough (bigger the wave the more energy it has). Measured in meters per second and shown as curly ‘a’.

Frequency - number of waves in a certain amount of time (normally a second). Measured in Hz (hertz) and shown as ‘f’

Question 3

Difference between longitudinal and transverse waves

Answer 3

Longitudinal waves are parallel to the direction of wave travel

Transverse waves are right angles to the direction of the wave travel

Question 4

Relationship between velocity, wavelength and frequency

Answer 4

Remember the triangle!

Velocity = frequency x wavelength

Frequency = velocity / wavelength

Wavelength = velocity / frequency

Question 5

Understand what is meant by wavefront

Answer 5

Wavefront is the imaginary surface use to represent the vibrating part of the wave.

Question 6

Huygens’ Construction

Answer 6

Huygen states that every point on a wave front acts as a source to secondary waves (wavelets). These waves propagate outwards/forwards forming a common tangent forming the next wavefront.

Question 7

Converging light

Diverging light

Parallel pencils of light

Answer 7

Converging light will eventually come to a focus point along the optical axis

Diverging light moves further away from the optical axis and will not form a focus point

Parallel light will never form a focus point along the optic axis but will also not move further apart from one another

Question 8

Define vergence

Answer 8

Vergence is the angle formed by rays of light that that are not parallel to one another (either converging or diverging)

measured in dioptres (D)

Question 9

Define curvature of wavefront

Answer 9

Curvature of wavefront is how curved the wave/ripple is. The curvature of a wavefront decreases the further away front the source.

Converging lenses (plus) increases curvature of wavefront to converge

Diverging lenses (minus) decreases curvature of wavefront to diverge

Question 10

Distinguish the difference between point source and extended source

Answer 10

Point source only forms umbra on a surface. Eg, a pinhole camera

Extended source forms both umbra and penumbra on a surface. Eg, the sun

Question 11

Properties of an image formed by a pinhole camera

Answer 11

The image will be:

Inverted

no distortion

image size will increase with length of the box

brightness of image will diminish as size increase