Question

Sitting in her parlour one night, Chitra sees the reflection of her cat in the living room window. If the cat makes an angle of ${{40}^{0}}$ with the normal, at what angle does Chitra see the reflected image of the cat?

Answer 1

Hint: When light from an object strikes a mirror, the light is reflected back and we see the image of the object. The formation of image by reflection of light follows the laws of reflection. Using the laws of reflection, we can answer the question.

Complete answer:
When a wave front strikes the interface of two media, the direction of the wave front changes and the wave front returns to the first medium from where it originated. This is called the reflection. To know how reflection occurs we need to know the laws of reflection.

Laws of reflection say that, the angle of incidence of the light and the angle of reflection of the light is equal to each other. The incident ray, the reflected ray and the normal to the point of incidence are in the same plane.

Now, the cat makes an angle of ${{40}^{0}}$ with the normal. So, the incident angle in the mirror is ${{40}^{0}}$ with the normal. Now, from the laws of reflection, we know that the angle of incidence is equal to the angle of reflection. Since, the cat makes an angle of incidence of ${{40}^{0}}$ with the normal, the image of the cat will also make an angle of ${{40}^{0}}$ with the normal. So, Chitra will see the reflected image of the cat at an angle of ${{40}^{0}}$ with the normal.

Note:
When light from an object is reflected in a mirror, the light is reflected again to the same medium. If the reflected light is in our line of sight or if the reflected ray enters our eyes we can see the reflection or the image. if our line of sight is different from the angle of reflection, then we cannot see the image of the object.