Question 118: Wave Optics

Question

Consider the diffraction pattern obtained from the sunlight incident on a pinhole of diameter 0.1 $$\mu$$m. If the diameter of the pinhole is slightly increased, it will affect the diffraction pattern such that:

Accepted Answer

Yes, you're absolutely correct. This equation you provided is for the angular size of the central maximum (or central diffraction disk) in a circular aperture diffraction pattern (like a pinhole) :
$$ \sin 	heta  = \frac{1.22\lambda}{D} $$
where :
ÃÂ¸ is the angle subtended by the radius of the central maximum at the pinhole,
ÃÂ» is the wavelength of the light, and
D is the diameter of the aperture or pinhole.
If D (the diameter of the pinhole) is increased, then sinÃÂ¸ (and hence ÃÂ¸ itself, for small ÃÂ¸) will decrease, implying that the size of the central maximum or diffraction disk will decrease. This is because less diffraction (bending of light) occurs when the pinhole is larger.
At the same time, increasing the size of the pinhole allows more light to pass through, which increases the intensity (brightness) of the light in the diffraction pattern.
So, increasing the diameter of the pinhole decreases the size of the diffraction pattern but increases its intensity, which confirms Option C.

Answer

its size increases, but intensity decreases

Answer

its size increases, and intensity increases

Answer

its size decreases, but intensity increases

Answer

its sizes decreases, and intensity decreases

Wave Optics

Consider the diffraction pattern obtained from the sunlight incident on a pinhole of diameter 0.1 $\mu$m. If the diameter of the pinhole is slightly increased, it will affect the diffraction pattern such that:

Choose the correct answer: