The power of a thin convex lens ( ang = 1.5) is + 5D. When it is placed in a liquid of refractive index anl, , then it behave as a concave lens of focal length 100 cm. The refractive index of the liquid anl, will be:

Question

The power of a thin convex lens ( ang = 1.5) is + 5D. When it is placed in a liquid of refractive index anl, , then it behave as a concave lens of focal length 100 cm. The refractive index of the liquid anl, will be: (A) 5/4 (B)  √3  (C) 4/3 (D) 5/3

Tardigrade Admin · Accepted Answer

Focal length of lens fa=(100/P) =(100/5)=20cm Focal length of lens in liquid f1=100cm from the formula (f1/fa)=((ang-1)/( (ang)en1-1 )) -(100/20)=((1.5-1)/( (1.5)x-1 )) -5=(0.5/( (1.5)x-1 )) ⇒ (1.5/x)-1=-0.1 (1.5/x)=0.9 x=(15/9)=(5/3)

Q. The power of a thin convex lens ( $_{a} n_{g}$ = 1.5) is + 5D. When it is placed in a liquid of refractive index $_{a} n l,$ , then it behave as a concave lens of focal length 100 cm. The refractive index of the liquid $_{a} n l,$ will be:

5/4

$3$

4/3

5/3

Q. The power of a thin convex lens ( a​ng​ = 1.5) is + 5D. When it is placed in a liquid of refractive index a​nl, , then it behave as a concave lens of focal length 100 cm. The refractive index of the liquid a​nl, will be:

5/4

3​

4/3

5/3

Focal length of lens fa​=P100​ =5100​=20cm Focal length of lens in liquid f1​=100cm from the formula fa​f1​​=(e​n1​a​ng​​−1)(a​ng​−1)​ −20100​=(x1.5​−1)(1.5−1)​ −5=(x1.5​−1)0.5​ ⇒ x1.5​−1=−0.1x1.5​=0.9 x=915​=35​

Q. The power of a thin convex lens ( $_{a} n_{g}$ = 1.5) is + 5D. When it is placed in a liquid of refractive index $_{a} n l,$ , then it behave as a concave lens of focal length 100 cm. The refractive index of the liquid $_{a} n l,$ will be:

$3$