Q13 of 26 Page 1

Answer the following:

(a)In what way is diffraction from each slit related to the interference pattern in a double slit experiment?


(b)When a tiny circular obstacle is placed in the path of light from a distant source, a bright spot is seen at the centre of the shadow of the obstacle. Explain, why.


(c)How does the resolving power of a microscope depend on (i) the wavelength of the light used and (ii) the medium used between the object and the objective lens?


(a) A double slit experiment can be thought of as the superimposition of two single slit diffraction pattern, one from each slit. The light from each slit can interfere constructively of destructively giving a pattern of bright and dark fringes.


(b)We know that diffraction occurs at the edges of objects. Here, light is diffracted from the edges of the circular obstacle and interfere constructively resulting in the formation of a bright spot at the center.


(c)The resolving power is given by



Therefore, the resolving power is


(i) inversely proportional to the wavelength of light used.


(ii)directly proportional the refractive index of the medium used between the object and objective.


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