Reflection in Physics

Reflection in Physics

Introduction

Reflection is a fundamental concept in optics, describing how light behaves when it encounters a reflective surface. It is crucial for understanding various optical phenomena, including the formation of images in mirrors. This page aims to explore the laws of reflection and review previous CBSE board exam questions on this topic.

Law of Reflection

The law of reflection states that:

  • The angle of incidence is equal to the angle of reflection.
  • The incident ray, reflected ray, and the normal all lie in the same plane.

Mathematically, this can be expressed as:

∠i=∠r \angle i = \angle r

CBSE Board Exam Questions on Reflection

Question 1

A ray of light strikes a plane mirror at an angle of 30 degrees with the normal. What is the angle of reflection?

Answer:

According to the law of reflection, the angle of incidence (∠i \angle i ) is equal to the angle of reflection (∠r \angle r ).

Thus, if ∠i=30∘ \angle i = 30^\circ , then:

∠r=30∘ \angle r = 30^\circ

Question 2

Explain the significance of the normal line in the reflection of light.

Answer:

The normal line is an imaginary line perpendicular to the surface at the point of incidence. It serves as a reference line for measuring the angles of incidence and reflection. The angles are always measured from the normal, ensuring accurate application of the law of reflection.

Question 3

Define the term 'virtual image' and how it is formed in a plane mirror.

Answer:

A virtual image is an image that cannot be projected on a screen as it appears to be located behind the mirror. When light rays reflect off a plane mirror, they do so in such a way that the reflected rays diverge, making it seem as though they originate from a point behind the mirror. This creates a virtual image that is upright and of the same size as the object.

Conclusion

Reflection is a key principle in understanding optics and light behavior. Mastering this concept is essential for tackling various problems and applications in physics. The discussions and questions provided exemplify how reflection can be examined in an examination context, reinforcing understanding through application.