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physics Advanced Subsidiary (AS) Level Physics.

Solved problems for the chapter:

Diffraction

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Refraction, Diffraction, and Interference of sound

1. Diffraction

1.1. Huygens principle

2. Interference

2.1. Wave amplification (Constructive interference)

2.2. Waves attenuation (Destructive interference)

3. Refraction of sound

3.1. Change in wavelength

3.2. Law of refraction

4. Forum

↓ Show theory [1] ↓

Detailed solution steps are available at:

https://en.openprof.com/wb/chapter:diffraction/4071/

Example 1.

Sound falls perpendicular to a horizontal barrier and passes through an opening whose width is twice the wavelength. At what angle to the vertical does the first minimum on the other side of the obstacle occur?

Example 2.

Diagram 1 shows a ripple tank experiment in which plane waves are diffracted through a narrow slit in a metal sheet. Diagram 2 shows the same tank with a slit of greater width. In each case, the pattern of the waves incident on the slit and the emergent pattern are shown.

Which action would cause the waves in diagram 1 to be diffracted less and so produce an emergent pattern closer to that shown in diagram 2?

increasing the speed of the waves by making the water in the tank deeper
reducing the length of the vibrating bar
increasing the frequency of vibration of the bar
reducing the amplitude of vibration of the bar

A pattern of waves was observed without being able to view the source of the waves. The pattern is represented in the diagram.

What can cause this pattern?

coherence only
diffraction only
interference only
diffraction and interference

Which diagram shows the diffraction of water waves in a ripple tank?

In which situation does diffraction occur?

A wave passes through an aperture.
A wave passes from one medium into another.
Waves from two identical sources are superposed.
A wave bounces back from a surface.

Which statement gives a condition that enables diffraction to occur?

Two waves of equal speed and frequency are travelling through the same part of a medium in opposite directions.
A wave is partially blocked by an obstacle.
Two coherent waves are superposed.
A source of waves moves towards a stationary observer.

Plane wavefronts in a ripple tank pass through a gap as shown.

Which property of the wave will be different at Q compared with P?

velocity
frequency
amplitude
wavelength

What is meant by diffraction?

Bending of waves round an obstacle.
Splitting of white light into colours.
Addition of two coherent waves to produce a stationary wave pattern.
Change of direction when waves cross the boundary between one medium and another.

The following statements describe the diffraction of waves passing through a narrow slit. Which statement is not correct?

Red light diffracts through a greater angle than blue light.
The angle of diffraction increases when the width of the slit decreases.
Diffraction can only be seen with light when the light is monochromatic.
Both transverse and longitudinal waves can be diffracted.

10.

Diffraction can be observed when a wave passes an obstruction. The diffraction effect is greatest when the wavelength and the obstruction are similar in size. For waves travelling through air, what is the combination of wave and obstruction that could best demonstrate diffraction?

sound waves passing a human hair
radio waves passing a copper wire
visible light waves passing a gate post
microwaves passing a steel post

11.

Diffraction is a term used to describe one aspect of wave behaviour. What does diffraction make possible?

the ability to hear high frequency and low frequency sound waves
the ability to hear sound through a brick wall
the ability to hear around corners
the ability to hear loud and quiet sounds

12.

Diagrams X and Y show the passage of water waves around an obstacle and through a gap. The thick lines are barriers to the waves and each thin line represents a wavefront.

Which statement is correct?

Diagrams X and Y both illustrate interference.
Only diagram X illustrates interference.
Only diagram Y illustrates diffraction.
Diagrams X and Y both illustrate diffraction.

13.

A water wave in a ripple tank is diffracted as it passes through a gap in a barrier. Which two factors affect the angle of diffraction of the wave?

the wavelength of the incident wave and the width of the gap
the wavelength and amplitude of the incident wave
the amplitude of the incident wave and the width of the gap
the amplitude and frequency of the incident wave

14.

What is an example of the diffraction of a wave?

microwaves passing the edge of a metal plate
sound waves diverging as they pass through air
laser light travelling along an optic fibre
light waves forming images on a cinema screen

15.

What happens when waves pass through a gap equal to their wavelength?

There is no diffraction and the wavelength stays the same.
There is no diffraction and the wavelength decreases.
There is diffraction and the wavelength stays the same.
There is diffraction and the wavelength decreases.

16.

In which situation does diffraction occur?

Waves from two identical sources are superposed.
A wave passes through an aperture.
A wave bounces back from a surface.
A wave passes from one medium into another.

17.

In an experiment, water waves in a ripple tank are incident on a gap, as shown.

Some diffraction of the water waves is observed. Which change to the experiment would provide a better demonstration of diffraction?

Increase the width of the gap.
Increase the wavelength of the waves.
Increase the amplitude of the waves.
Increase the frequency of the waves.

18.

Which statement must be true for diffraction to occur when a wave passes through a gap?

The wave is progressive.
The wave has a long wavelength.
The wave is able to travel in a vacuum.
The wave has a large amplitude.

19.

A water wave passes through a gap between two barriers. The wavefronts spread out as shown.

What is the name of this phenomenon?

interference
diffraction
superposition
coherence

20.

A hill separates a television (TV) transmitter from a house. The transmitter cannot be seen from the house. However, the house has good TV reception.

By which wave effect at the hill could the TV signal reach the house?

interference
reflection
diffraction
coherence

21.

Water waves in a ripple tank are made to pass through a small gap as shown. Which diagram shows the waves after they have passed through the gap?