DIFFRACTION 2
Where necessary take the velocity of light as = 3x108
ms-1 and the velocity of sound as 330ms-1
1. (a) Draw a
diagram to show how the intensity of diffracted light varies with the angle of
diffraction for light passing through a single slit.
(b) a single
slit is placed vertically on a spectrometer table and monochromatic light
passing through it is observed with the telescope. Describe what you see.
(c) what
would be observed if white light is used instead
2. A diffraction grating with 600 lines per
mm is placed in a beam of monochromatic light. The angle of diffraction for the
first order maximum is 25o.
Calculate the wavelength of the light.
3. Explain carefully the effect on the
spectrum observed by a plane transmission diffraction grating if the ruled face
is presented to the incident light rather than the unruled face.
4. A
trumpeter standing inside a narrow doorway plays a note with a frequency of 500
Hz. If the doorway is 0.75 m wide calculate the angle of diffraction for the
first minimum of the diffraction pattern produced.
5. How could you tell the difference between a CD and a DVD simply by
looking at the diffraction pattern produced by a white light source?
6. Light from a certain fluorescent lamp is
found to consist of only two wavelengths, 450 nm and light of a longer
wavelength. When the light is passed through a given diffraction grating it is
found that the third order for the shorter wavelength has the same diffracted
angle as the second order for the longer wavelength. Calculate:
(a) the wavelength of the light with the
longer wavelength
(b) the grating spacing if the angle of
diffraction in this case is 20o
7. Water waves of wavelength 4m meet a
narrow entrance to a harbour. If the entrance is 10m wide calculate the
separation between the central maximum and the first minimum on the beach if
the distance from the harbour mouth to the beach is 250m.
8. A diffraction grating having 6300 lines
per centimetre is set up on the table of a spectrometer and is illuminated
normally with monochromatic light. Bright images are formed on the cross-wires
of the telescope at the following scale settings: 107.6°, 130.0° and 152.4°.
Explain this, and calculate the wavelength of the light.