Name: Virtual Image
Uploaded: 2019-07-19
Duration: 47 s
Description: Here is a demonstration of the virtual and real images formed by a mirror. This video also explains the process of formation of real and virtual images.

Question

Explain the following with the help of a ray diagram, in relation to the two main types of spherical lenses:

(a) Principal focus
(b) Focal length

Accepted Answer

(a) Principal focus:
Convex lens:- In a convex lens, the parallel rays of light passing through the lens converge at a point in front of the lens after refraction. This point is known as the focus of the lens. In the following figure, F is the focus.

Concave lens:- In a concave lens, the parallel rays of light passing through the lens diverge and when these rays are produced backwards, they appear to meet at a point behind the lens. The point is called the focus of the concave lens. In the following figure, F is the focus.

(b) Focal length:-
Convex lens:- The focal length of a convex lens is the distance between the focus F and the optical center (O). In the above figure of the convex lens, OF is the focal length.
Concave lens:- The focal length of a concave lens is the distance between the focus F and the optical center (O). In the above figure of the concave lens, FO is the focal length.
The focal length is measured in centimeters or meters.

Explain the following with the help of a ray diagram, in relation to the two main types of spherical lenses:

(a) Principal focus
(b) Focal length

Important Questions on Light

Learn and Prepare for any exam you want !

Explain the following with the help of a ray diagram, in relation to the two main types of spherical lenses: (a) Principal focus (b) Focal length

Important Questions on Light

Learn and Prepare for any exam you want !

Explain the following with the help of a ray diagram, in relation to the two main types of spherical lenses:

(a) Principal focus
(b) Focal length