Home
Class 12
PHYSICS
Find the focal length of the lens used t...

Find the focal length of the lens used to focus an image of distant object on focal plane of the lens if the radius of central bright dot is `5 mum`, when it illuminated by ray of wavelength 400 nm and the radius of the circular aperture is 2.5 cm.

Text Solution

Verified by Experts

`r_0=(0.61 lamda f)/a`
`r_0=5 times 10^-6m`
`lamda=400 times 10^-9 m`
`a=2.5 cm`
`f=0.512`
Promotional Banner

Similar Questions

Explore conceptually related problems

A convex lens has a focal length of 20 cm. It is used to form an image of an object placed 15 cm from lens. The image is

A biconvex lens of focal length f forms a circular image of radius r of sun in focal plane . Then which option is correct

Find the focal length of a convex lens which produces a virtual image at 10 cm from the lens when an object is placed at 5 cm from the lens.

A lens ( focal length 50 cm ) forms the image of a distant object which subtends an angle of 2 milliradian at the lens. What is the size of the image ?

The focal length of a convex lens is 20 cm . If an object of height 2 cm is placed at 30 cm from the lens , Find the magnification produced and height of the image

Find the focal length of a convex lens which produces a real image at 60 cm from the lens when an object is placed at 40 cm in front of the lens.

Find the distance of an object from a convex lens if image is two times magnified. Focal length of the lens is 10cm