(i) What is a continuous emission spectrum? Name one source of light which produces such a spectrum.
(ii) Explain in brief why dark lines are observed in the solar spectrum.
(i) Continuous emission spectrum: It consists of continuous bright spectral lines without any gap. It is produced by a source in bulk, e.g. tungsten filament, live candle etc.
(ii) The dark lines are observed in the solar spectrum because it is absorption Spectrum. The spectrum obtained when light from a luminous body falls on an absorbing material is called the absorption spectrum. The absorption spectrum contains dark part/lines. It is characteristic of absorbing body.
The spectrum of the sun is line absorption spectrum.
(i) What are coherent sources?
(ii) In young’s double slit experiment, what is the path differences between the two light waves forming 5th bright band (fringe) on the screen?
(i) In case of polarized light, what is means by the plane of polarization?
(ii) Find refractive index of glass if its polarising angle is 60°.
(i)Explain the statement: “Angular magnification of a compound microscope in normal use is 30”.
(ii) State how the resolving power of an astronomical telescope can be increased.
In Millikan’s oil drop experiment, the two plates are 2 cm apart. When a potential differences of 2355 V is applied between them, an oil drop of radius 1μm is found to remain suspended. Calculate the number of excess electrons on the drop,
[Density of oil = 900 kg/m 3 = Density of air may be ignored]