A convex lens of diameter 8.0 cm is used to focus a parallel beam of light of wavelength 620 nm. If the light be focused at a distance of 20 cm from the lens, what would be the radius of the central bright spot formed ?

Parallel beam of light of wavelength 420 nm is focused on a screen at a distance of 50 cm from the lens. What would be the radius of the central bright spot formed? Diameter of the lens is 10 cm.

A parallel beam of monochromatic light of wavelength 5900Å falls normally on a convex lens of diameter 10cm which focusses the light on a flat normal screen located at a distance of 20cm from the lens. What would be the radius of the central bright spot formed on the screen?

Light of wavelength 620 nm goes through a pinhole of diameter 0.1 mm. Screen is placed at a distance 5 m from the hole. What will be the radius of the central bright spot formed ?

Light of wavelength 560 nm goes through a pinhole of diameter 0.20 mm and falls on a wall at a distance of 2.00 m. What will be the radius of the central bright spot formed on the wall ?

A beam of light of wavelength 590 nm is focussed by a converging lens of diameter 10.0 cm at a distnce of 20 cm from it. find the diameter of he disc image formed.

A convex lens is used to focus the rays from the far off light bulb at a distance of one meter from the lens. What should be the focal length of the lens ? Draw a ray diagram to show the formation of image.

The focal length of convex lens is 20 cm. If an object of height 4 cm is placed at a distance of 30 cm from the lens, find: The magnification produced by the lens.

The size of the image of an object, which is at infinity, as formed by a convex lens of focal length 30 cm is 2 cm. If a concave lens of focal length 20 cm is placed between the convex lens and the image at a distance of 26 cm from the convex lens, calculate the new size of the image

A single slit of width 0.20 mm is illuminated with light of wavelength 500 nm . The observing screen is placed 80 cm from the slit. The width of the central bright fringe will be