QQuestion
In the case of refraction if the angle of incidence is 45° and the refracted ray makes an angle of 60° with the normal, what will be the value of the angle of deviation?
If an object of 6 cm in length is placed at a distance of 2.4 cm in front of a convex lens, the image is formed at a distance of 4.8 cm from the lens. What are linear magnification and the length of the image? [1 + 2]
✓Answer
Angle of incidence (i) = 45º
Angle of refraction (r) = 60º
Angle of deviation (δ) = i − r
= 45º – 60º = −15º
The negative sign indicates that the deviation is towards the normal.
Given:
Object length (h) = 6 cm
Object distance (u) = – 2.4 cm
Image distance (v) = 4.8 cm
(i) Linear Magnification (m) = 4.8\over -2.4 = -2
(ii) Length of the Image = m × h = – 2 × 6 cm = -12 cm
The negative sign indicates that the image is inverted.
OR
Speed of light in vacuum = 3 × 105 km/s
Speed of light in glass = 2 × 105 Km/s
Speed of light in water = 2.25 × 105 Km/s
μglass = 3 × 10^5\over 2 × 10^5 = 1.5
μwater = 3 × 10^5\over 2.25 × 10^5 = 4/3
Ratio = μglass : μwater = 1.5 : 4/3 = 9:8
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