Ex. 8.2
1. An interference pattern is produced when two coherent waves overlap.
a) If a minimum is produced, what are the possible values for the path difference? (1)
b) If a maximum is produced, what are the possible values for the path difference? (1)
3.
Light waves from two slits S1 and S2 produce a bright fringe at P.
The light has a wavelength of 400 nm.
Calculate the path difference S1P - S2P. (2)
11.
Two coherent water waves are produced by dippers at A and B.
An interference pattern is observed with a minimum at P.
If the distances are as shown, explain which of the following values could be the wavelength of the waves: 2, 3, 4 or 6 cm. (3)
Ex. 8.3
4. Light of wavelength 600 nm is passed through a grating.
The grating has 2.5 x 105 lines per metre.
Calculate the angle at which the first maximum appears. (3)
5. An interference fringe is produced by passing green light through a grating.
What will each of these changes do to the fringe spacing?
a) Increasing the distance between the grating and the screen
b) using blue light instead of green
c) increasing the irradiance of the light source
d) increasing the number of lines per mm on the grating.(4)
Past Paper Questions
7. (a) (i) An interference pattern is produced by directing laser light through a grating. The grating has a separation of 5.0 x 10-6 m between the slits. The angle θ between the central maximum and the 2nd order maximum is 14°.
Calculate the wavelength of light produced by the laser. (2)
(ii) A pupil suggests that a more accurate value for the wavelength of the laser light can be found if a grating with a slit separation of 2.0 x 10-6 m is used. Explain why this suggestion is correct. (2)
(b) The laser is replaced by a source of white light.
Explain:
(i) why the central maximum is white (1)
(ii) why the other maxima are in the form of continuous spectra.(1)
13.
Two loudspeakers are connected to the same signal generator.
(a) (i) When a sound level meter is moved from P to T, maxima and minima of sound level are detected.
Explain, in terms of waves, why the maxima and minima are produced. (2)
(ii) The sound level meter detects a maximum at P.
As the sound level meter is moved from P, it detects a minimum then a maximum then another minimum when it reaches Q.
Calculate the wavelength of the sound used. (2)
(b) The sound level meter is now fixed at Q.
The frequency of the output from the signal generator is increased steadily from 200 Hz to 1000 Hz.
(i) What happens to the wavelength of the sound as the frequency is increased? (1)
(ii) Explain why the sound level meter detects a series of maxima and minima as the frequency of the output is increased.(2)
Total marks = (27)