Question
The tip of a needle does not give a sharp image on a screen. This is due to
polarisation
interference
diffraction
None of these
Solution
C.
diffraction
As the size of tip of the needle is very small ( because its a point ) and it comes under the range of wavelength of light, so the ray coming from back side of needle ( i.e consider needle's tip just blocking a ray of light) will bend across the tip.
And hence on screen, that ray will also give brightness near so formed image of needle's tip, hence reducing the original sharpness of the needle's tip.
The tip of a needle does not give a sharp image, it is due to diffraction.
