Physics
A ray of light after refraction through a lens emerges parallel to the principal axis of the lens. The incident ray passes through :
- its optical centre
- its first focus
- its second focus
- the centre of curvature of the first surface.
Refraction Lens
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Answer
its first focus
Reason — When the incident ray passes through the first focus then it emerges parallel to the principal axis of the lens after refraction. We can understand this better with the help of diagrams given below —
Convex Lens
Concave Lens
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Related Questions
A convex lens in its upper part has a prism with its base …………… and a concave lens in its upper part has a prism with its base …………… :
- downward, upward
- upward, downward
- upward, upward
- downward, downward
The correct differences between a convex and concave lens are :
(a) convex lens is thin in the middle and concave lens is thick in the middle.
(b) convex lens converges the incident rays towards the principal axis whereas concave lens diverges
(c) convex lens has a virtual focus and concave lens has a real focus.
- (a)
- (c)
- (a), (b) and (c)
- (b)
A ray of light incident on a lens parallel to its principal axis, after refraction passes through or appears to come from :
- its first focus
- its optical centre
- its second focus
- the centre of curvature of its second surface.
A lens is called equi-convex or equi-concave when :
- the radius of curvature of first surface of lens is greater than the radius of curvature of the second surface.
- the radius of curvature of the second surface of the lens is greater than the radius of curvature of the first surface.
- the radius of curvature of the two surfaces of the lens are equal.
- none of the above