H211 Waves

Question 1

What happens in progressive waves?

Answer 1

In progressive waves, energy is propagated from one place to another in the direction of wave travel without bulk movement of medium.

Question 2

Define wavefront.

Answer 2

A wavefront is an imaginary line that joins all the points of a wave that are at the same phase.

Question 3

Define speed of a progressive wave.

Answer 3

The speed of a progressive wave is the speed at which energy is transferred.

Question 4

What is the formula for wave speed?

Answer 4

v = wavelength x frequency

Question 5

Define wavelength.

Answer 5

The wavelength of a wave is the minimum distance between two points with the same phase.

Question 6

Define frequency

Answer 6

Number of crests passing a point per unit time

Question 7

Define phase.

Answer 7

Phase is an angular measure of the fraction of a cycle completed by the oscillating mass.

Question 8

Define phase difference.

Answer 8

Phase difference is the measure of how much an oscillation is out of step with another oscillation at the same instant in time.

Question 9

What is antiphase?

Answer 9

Paticles are in antiphase when they execute motions that are out of phase by pi rad or 180 degrees. (The particles have equal but opposite displacements, velocities and accelerations)

Question 10

Define transverse waves.

Answer 10

A transverse wave is one where the oscillations are normal to the direction of energy propogation.

Question 11

Define longitudinal wave.

Answer 11

A longitudinal wave is one where the oscillations are parallel to the direction of energy propogation.

Question 12

Define intensity of a wave.

Answer 12

The intensity of a wave is the rate of energy flow per unit area that is perpendicular to the direction of wave propagation.

Question 13

What is the formula for intensity?

Answer 13

I = Power/Area

Question 14

What is the relationship between intensity and amplitude?

Answer 14

Intensity is directly proportional to the square of amplitude.

Question 15

State the formula for intensity for spherical wavefronts.

Answer 15

I = P/4pir^2
I is directly proportoinal to 1/r^2

Spherical wavefronts is when energy is from a point source and is radiated outwards uniformly in all directions.

Question 16

State the formula for intensity for planar wavefronts.

Answer 16

I = P/A

Planar wavefronts are waves that travel along a collimated beam

Question 17

State the formula for intensity for circular wavefronts.

Answer 17

I = P/2pir
I is directly proportional to 1/r

Circular wavefronts is when waves from a point source is confined to a 2D surface.

Question 18

What is a polarised wave?

Answer 18

In a polarised wave, the oscillations are along one direction only, in a single plane that is normal to the direction of energy transfer of the wave.

Only transverse waves can be polarised.

Question 19

What is Malus’ Law?

Answer 19

Intensity is directly proportional to cos^2 x
I = I0 cos^2 x

Question 20

What does Malus’ Law state?

Answer 20

Malus’ Law states that the intensity of a beam of plane polarised light after passing through a polariser varies with the square of cosine of the angle through which the polariseris rotated from the position that gives maximum intensity. (From RI notes idk if in syllabus)

Question 21

What happens when polarised light reaches another polariser?

Answer 21

The component of the displacement that is parallel to the transmission axis is allowed to pass while the component that is perpendicular to the tranmission axis is absorbed by the polariser.
A = A0 cos x