A glass lens of refractive index `1.45` when immersed in a transparent liquid becomes invisible. Under what condition does it happen ?

Explanation

To determine the condition under which a glass lens of refractive index 1.45 becomes invisible when immersed in a transparent liquid, we can follow these steps:

### Step 1: Understand the Concept of Refraction
Refraction occurs when light passes from one medium to another and changes speed, which causes the light to bend. The refractive index (n) of a medium is a measure of how much the speed of light is reduced inside that medium compared to the speed of light in a vacuum.

### Step 2: Define the Condition for Invisibility
A lens becomes invisible when there is no refraction occurring at the boundary between the lens and the surrounding medium. This happens when the refractive indices of the two materials are equal.

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