Science — CBSE Class 10 board question

The two laws of refraction of light are:

1. The incident ray, the refracted ray, and the normal to the interface of the two transparent media at the point of incidence, all lie in the same plane.

1. The ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant for a given pair of media and given colour of light. This is known as Snell's law.

$$\frac{\sin i}{\sin r} = \text{constant}$$

Source: Chapter 9, Section 9.3.1

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• Both laws must be stated for full 2 marks (1 mark each).
• Law 1 is about geometry (coplanarity); Law 2 is Snell's law — always name it.
• Writing the formula for Snell's law strengthens the answer but is not mandatory for 2 marks.
• Avoid writing about refractive index here — the question only asks for the laws, not their implications.