Question

A symmetrical convergent lens is having focal length equal to twice the radius of curvature of its surface then refractive index of material of lens is equal to​

Answer 1

Answer:

correct Answer is C:  3/2

explanation:

Convex lens focal length=R

Symmetrical lens=Hence=R1=R2=R

By sigh conventions convex lens: R1=+R

R2= -R

Lens makers formula :

1/f=(n-1)[1/R1-1/R2]

1/R=(n-1)[1/R+1/R]

1/R=(n-1)[2/R]

1=2n-2

2n=3

n=3/2 =1.5

Answer 2

Answer:

Given:f=R

1

=−R

2

=R(let)

from lens maker's formula

f

1

=(μ−1)(

R

1

1

−

R

2

1

)

R

1

=(μ−1)

R

2

μ=

2

3