Physics
The focal length of a lens depends upon :
- the refractive index of the material of lens relative to its surrounding medium
- the amount of light entering the lens
- the radius of curvature of the two surfaces of lens
- both (1) and (3)
Refraction Lens
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Answer
both (1) and (3)
Reason — The focal length of a lens depends upon two factors:
- The refractive index of the material of lens relative to its surrounding medium.
- The radii of curvature of the two surfaces of lens.
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Related Questions
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
If a lens is placed in water instead of air, its focal length :
- increases
- decreases
- remains the same
- can both increase or decrease
If half part of a convex lens is covered, the focal length …………… but the intensity of the image ……………
- increases, decreases
- decreases, increases
- does not change, increases
- does not change, decreases