Waves 1

Question 1

define a progressive wave. define a standing wave

Answer 1

• progressive wave: transfers energy and shape

- standing wave: energy is trapped in packets

Question 2

outline the differences between transverse and longitudinal waves

Answer 2

• transverse: oscillations perpendicular to the direction of wave travel
• longitudinal: oscillations parallel to the direction of wave travel

Question 3

define displacement. define amplitude

Answer 3

• displacement: the distance of a particle from its equilibrium position
• amplitude: the maximum displacement of a particle

Question 4

define wavelength, frequency and period

Answer 4

• wavelength: the distance between two adjacent peaks of a wave
• frequency: the number of waves that pass a point per unit time, f=1/period
• period: the time taken for one complete oscillation

Question 5

define phase difference and path difference

Answer 5

phase difference: the amount in radians that two points on a wave differ (or on two different waves)
path difference: the amount in metres that two points on a wave differ (or on two different waves)

Question 6

what is the equation for wave speed

Answer 6

v=fλ

for EM waves, c=fλ

Question 7

outline reflection key points

Answer 7

• a wave hitting a boundary between media and changing direction, but staying in the original medium
• angle of incidence = angle of relection

Question 8

outline refraction key points

Answer 8

• a wave reaching the boundary between two media and changing speed, therefore changing direction
• when light slows down (e.g Air to Glass) it bends AGAINST the normal
• when light speeds up (e.g Glass to Air) it GOES AWAY from the normal

Question 9

outline diffraction key points

Answer 9

-when a wave enters a gap, if the gap size is equal to or smaller than the wavelength, the wave spreads out.
-can also occur when a wave travels around an obstacle, if the obstacle is a similar size to the wavelength
helps radio waves reach places behind hills

Question 10

outline polarization key points

Answer 10

• unpolarized waves are waves where the oscillations are in all directions
• polarizing filters make sure only waves with oscillations in one direction can get through
• only transverse waves can be polarized
• used in sunglasses

Question 11

what is the formula for intensity of a wave, and what is it proportional to

Answer 11

Intesity = Power/Area

Intensity ∝ amplitude²

Question 12

what are the approximate wavelengths of each wave in the EM spectrum

Answer 12

gamma: <1pm
x-ray: 1pm-10nm
ultraviolet: 10nm-400nm
visible light: 400nm-700nm
infra-red: 400nm - 1mm
microwaves: 1mm-1m
radio waves: >1m

Question 13

how do you calculate the refractive index of a medium

Answer 13

n = speed of light in a vacuum/speed of light in the medium