(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) 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) Plane of Polarization: The plane containing the direction of propagation of light and perpendicular to the vibration is called plane of polarization. There are no vibrations of electric vector in the plane of polarization.
(ii) According to the Brewster law the refractive index of the glass ( w.r.t. air) is
ang = tan θP ;
where θP is the polarizing angle
θP = 60°, is the required refractive index.
(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]