Question

b. State the nature of the lens and focal length if it's power is +4D.
Draw diagrams of pulley systems having velocity ratio i. 6 and ii.3.
C.​

Answer 1

(a) The power of a lens is defined as the reciprocal of its focal length.

(b) The ray diagram is shown for the formation of image of an object situated at a point in between 2f
1
​
and f
1
​
distances from the optical centre of the concave lens.
A diminished, virtual and erect image formed is between focus f
1
​
and optical centre O.

(c) When light falls perpendicular to an interface of two media, it enters into the second media without any refraction. Here the angle of incidence is 0°. For such angle of incidence, bending of light at the interface of the media does not take place.