worksheet_15.pdf

15 Work Worksh shee eett (AS) Data needed to answer questions can be found in the Data, formulae and relationships sheet. 1

The diagram shows water waves passing through a gap.

What property of waves is being demonstrated? A B C D 2

[1]

diffraction interference superposition  polarisation

The diagram show two loudspeakers connected to the same signal generator.

A girl walks from position A to position B. Which statement describes what she will hear and gives the correct reason? A B C D

[1]

A rise and fall in the loudness as the waves go in and out of phase. A rise and fall in the pitch as the waves go in and out of phase. A steady loud sound because the waves are in phase. A steady soft sound because the waves are out of phase.

AS and A Level Physics

Original material © Cambridge University Press 2010

1

15 Worksheet (AS) 3

The graph shows two waves. Displacement

Time

Which statement is correct? A B C D 4

[1]

The waves are coherent and in phase. The waves are coherent but out of phase. The waves are incoherent and out phase. The waves are incoherent but in phase.

A student sets up a experiment to show interference of light. He uses two small red LEDs as the light sources. Which of the following explains why he will not be able to show interference? [1] A B C D

The light from an LED does not does not have a single wavelength. The light from an LED does not have a constant frequency and so will not be in phase. The light from the two LEDs will not be in phase. The light from the two LEDs will not be coherent.

AS and A Level Physics

Original material © Cambridge University Press 2010

2

15 Worksheet (AS) 5

An experiment is set up to demonstrate interference from different types of elect romagnetic radiation. The apparatus is shown below and the dimensions are kept constant for all types of radiation.

Which type of radiation will produce fringes which are the closest together? A B C D 6

 blue light infrared radiation red light ultraviolet radiation

a

Describe what is meant by the diffraction of a wave.

b

Electromagnetic radiation of frequency 7.5 × 109 Hz is directed towards a slit of width 6.0 cm.

[1]

Determine the wavelength of the radiation. ii  Explain whether or not the radiation will be diffracted at the slit.

[2] [1]

i

7

Explain what is meant by coherent sources.

8

The diagram below shows the displacement–time graphs for two waves

a b

[1]

[1] A and B.

What is the phase difference between the two waves? The two waves A and B are combined. Name combined. Name the type of interference that will occur.

AS and A Level Physics

Original material © Cambridge University Press 2010

[1] [1]

3

15 Worksheet (AS) 9

The diagram below shows an arrangement used to demonstrate the interference of of water waves.

a

b

10

Constructive interference occurs at point A. What is the path difference of the waves from the gaps S1 and S2? The water waves have a wavelength of 3.0 cm. Determine the path difference for the waves arriving at point B. Name the type of interference taking place at this point.

b

c

Explain why the receiver registers a series of maxima and minima. The wavelength of the microwaves is 2.8 cm. The separation between the slits is 4.0 cm and the receiver is a distance of 80 cm from the slits. Calculate the separation between adjacent maxima. Describe the effect on your answer to b when: i ii

the separation between the slits is halved the distance between the slits and the receiver is doubled.

[3]

[3] [1] [1]

Monochromatic light is incident normally at a diffraction grating with 60 lines per mm. The tenth-order maximum is observed at an angle of 19°. Determine: a b

12

[3]

A microwave source is directed towards a metal plate with two narrow vertical slits. A receiver is slowly moved along the line XY as shown in the diagram.

a

11

[1]

the spacing (in metres) between the centres of the adjacent lines on the diffraction diffraction grating the wavelength of incident light.

Yellow light of wavelength 5.5 × 10−7 m is incident normally at a diffraction grating with 300 lines per mm. Calculate the angle between the first-order and second-order maxima.

AS and A Level Physics

Original material © Cambridge University Press 2010

[2] [3]

[5]

4

15 Worksheet (AS) 13

14

Blue light of wavelength 4.5 × 10−7 m is incident normally at a diffraction grating with 100 lines per mm. Calculate the maximum number of orders that can be observed.

[4]

Answer the following questions with supporting calculations. You are given a diffraction grating with 40 lines per mm. a

b

The diffraction grating is mounted on an instrument that can measure angles to within ±0.1°. Can this instrument be used to determine the individual wavelengths of spectral lines of wavelengths 589.6 nm and 589.0 nm? [6] White light is incident normally at the grating. Estimate the angle between the extreme ends of the spectrum for the tenth-order maxima. [4]

Total:

AS and A Level Physics

48

Score:

Original material © Cambridge University Press 2010

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