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WBJEEA plano-convex lens is made of a material of refractive index n. When...
A plano-convex lens is made of a material of refractive index n. When a small object is placed 30 cm away in front of the curved surface of the lens, an image of double the size of the object is produced. Due to reflection from the convex surface of the lens, another faint image is observed at a distance of 10 cm away from the lens. Which of the following statement(s) is (are) true?
Solution:
1v-1u=1f
160-1(-30)=1f⇒ f=20cm ...(i)
Also 1f=(n-1) (1R-1∞)=(n-1)R ....(ii)
For reflection from convex mirror (curved surface)
1v+1u=1f=2R ....(iii)
R = 30 cm
From (i), (ii) and (iii)
n=2.5,
Faint image erect and virtual
1v-1u=1f
160-1(-30)=1f⇒ f=20cm ...(i)
Also 1f=(n-1) (1R-1∞)=(n-1)R ....(ii)
For reflection from convex mirror (curved surface)
1v+1u=1f=2R ....(iii)
R = 30 cm
From (i), (ii) and (iii)
n=2.5,
Faint image erect and virtual
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