Acertain thin lens is made of glass with refraction index =1.500. in air, where the index of refraction is 1.000, the lens has focal length =11.5 cm.

what is the focal length of the lens when immersed in ethyl alcohol, where the index of refraction is 1.360?

The focal length of the lens in ethyl alcohol is 41.07 cm.

Explanation:

Given that,

Refractive index of glass= 1.500

Refractive index of air= 1.000

Refractive index of ethyl alcohol = 1.360

Focal length = 11.5 cm

We need to calculate the focal length of the lens in ethyl alcohol

Using formula of focal length for glass air system

Using formula of focal length for glass ethyl alcohol system

Divided equation (II) by (I)

Where, = refractive index of glass

= refractive index of air

= refractive index of ethyl

Put the value into the formula

Hence, The focal length of the lens in ethyl alcohol is 41.07 cm.

a electromagnetic waves

0.11 m/s and 0.28 m/s should be correct