Chapter 5: REFRACTION
THROUGH A LENS
Refraction through a lens
Q 1.
(i) What is a lens?
(ii) Name two kinds of lens.
(iii) What is a convex or converging lens?
(iv) Name and draw three kinds of convex lens.
(v) What is convex or diverging lens?
(vi) Name and draw three kinds of convex lens.
ANSWERS:
(i) A lens is a transparent refracting medium bounded by either two spherical surfaces, or
one spherical surface and the other surface plane.
(ii) Two kinds of lens are- Convex or converging lens and Concave or diverging lens
(iii) A lens which is thick in the middle and thin at the periphery is a convex lens. It is a
converging lens because light converges o passing through it.
(iv) Three kinds of convex lens are:
(v) A convex lens is a lens which is thin at the middle and thick at the periphery. It is a
diverging lens because light diverges or spreads on passing through it.
(vi) The three kinds of concave lens are:
, Q 2.
(i) Convergent action of a convex lens
(ii) Divergent action of a concave lens
ANSWERS:
(i)
A convex lens can be considered to be made of a rectangular glass block in the middle
and two prisms joined base to base. When a beam of light is incident on it, it converges
to a point.
(ii)
(iii) A concave lens can be considered to be made up of a rectangular glass block in the
middle and two prisms joined apex to apex. When a parallel beam of light in incident on
it, it appears to meet or diverge from a point.
Q 3.
(i) Centre of curvature
(ii) Radius of curvature
(iii) Principal axis
(iv) Optical Centre (for thin lens)
THROUGH A LENS
Refraction through a lens
Q 1.
(i) What is a lens?
(ii) Name two kinds of lens.
(iii) What is a convex or converging lens?
(iv) Name and draw three kinds of convex lens.
(v) What is convex or diverging lens?
(vi) Name and draw three kinds of convex lens.
ANSWERS:
(i) A lens is a transparent refracting medium bounded by either two spherical surfaces, or
one spherical surface and the other surface plane.
(ii) Two kinds of lens are- Convex or converging lens and Concave or diverging lens
(iii) A lens which is thick in the middle and thin at the periphery is a convex lens. It is a
converging lens because light converges o passing through it.
(iv) Three kinds of convex lens are:
(v) A convex lens is a lens which is thin at the middle and thick at the periphery. It is a
diverging lens because light diverges or spreads on passing through it.
(vi) The three kinds of concave lens are:
, Q 2.
(i) Convergent action of a convex lens
(ii) Divergent action of a concave lens
ANSWERS:
(i)
A convex lens can be considered to be made of a rectangular glass block in the middle
and two prisms joined base to base. When a beam of light is incident on it, it converges
to a point.
(ii)
(iii) A concave lens can be considered to be made up of a rectangular glass block in the
middle and two prisms joined apex to apex. When a parallel beam of light in incident on
it, it appears to meet or diverge from a point.
Q 3.
(i) Centre of curvature
(ii) Radius of curvature
(iii) Principal axis
(iv) Optical Centre (for thin lens)
