Question

The lens is made up of which glass

• A. Ordinary Glass
• B. Pyrex Glass
• C. Flint Glass
• D. Cobalt Glass

Answer 1

The correct option is C

Flint Glass

The explanation for the correct answer:

Option C: Flint Glass

1. A lens is an optical device that disperses or focuses light through the refraction process.
2. The material used for the lens needs to have a high refractive index and low Abbe number.
3. Flint Glass is a material that has these specific properties and is used to make a lens that has a refractive index $1.65$ and abbe number is nearly $50$
4. Hence, option C is correct.

The explanation for the incorrect answer.

Option A: Ordinary glass

1. The Refractive index of ordinary glass is $1.5$ which is considered to be low, so we don't use ordinary glass in lens making.
2. Hence, option A is incorrect.

Option B: Pyrex glass

1. The Refractive index of Pyrex glass is $1.47$ which is considered to be low, so we don't use ordinary glass in lens making.
2. Hence, option B is incorrect.

Option D: Cobalt glass

1. Even though cobalt glass has a high refractive index of $2.13$, the abbe number is also high, so it is not used in making lenses.
2. Hence, option D is incorrect.

Thus, option C is the correct answer.