Mirrors And Reflection

What is a Mirror?

What can mirrors do and how can you observe various reflections using a mirror? Try a simple experiment of mirrors and reflection with a friend of yours to prove one of the most important laws, the law of reflection. For this experiment, you need

  1. A friend who is the same height as you
  2. A small mirror, even as small as 10 x 15 cm in size is enough
  3. Marking tape
  4. A protractor to measure angles
  5. A nice wall with lots of space in front of it

The Process:

Place the mirror on some spot on the wall. Use marking tape from the center of the mirror, straight down to the floor as shown in the image below.

Using the wall as an anchor, and the point of the mirror’s position on the floor, create a 90o line using marking tape and protractor.

Now you and your friend should adjust yourselves such that you are able to see your friends face in the mirror and your friend can see your face in the mirror. Mark your positions on the floor using the marking tape. Now join your position to the position of the mirror using marking tape. Do the same for your friend.

Using the protractor measure the angles between your position line and the ninety-degree line and record it. Now measure the angle between your friend’s position line and the ninety-degree line and record. Are they the same? Accommodating experimental errors, they should be the same.

If we call your position line the incident ray, your friend sees your reflection in the mirror, which is the reflected ray. This is a simple technique of using mirrors and reflection of an object which can be carried out at your home. According to the law of reflection of light, the angle of incidence is always equal to the angle of reflection. And we have just proved this using our experiment.

Does light always travel in a straight line?

  • We know light travels in a straight line, but what if we have to change the path of light?
  • Can light change its direction on its own? No.
  • We can change the direction of light with the help of mirrors and lens.

Reflection in Plane Mirrors:

  • The candle that appears in the mirror is the image.
  • The candle placed in front of the mirror is the object.
  • Move the object away from the mirror. The image will always remain upright/erect.
  • Place a screen behind and in front of the mirror, the image of the candle cannot be obtained on the screen. What does this mean? We will discover this later in this article.

Right or Left:

  • Left side appears on the right side in the mirror and vice versa
  • This is why the word an ambulance is written in reverse order i.e. ECNALUBMA – AMBULANCE.

Spherical Mirrors:

  • The inner side of the spoon acts as a concave mirror and outer side of the spoon acts a convex mirror.
  • When the image obtained on the screen appears exactly the same as the object, it is known as upright image and when the image obtained is upside down, it is known as inverted image.
  • When an image is obtained on the screen kept in front or behind the mirrors/lens, it is known as real image and when the image is not obtained on the screen, it is known as a virtual image.

Comparison of image in plane, convex and concave mirrors:

Images formed by Lenses:

  • Concave lens – The lens, which is thinner in the middle and thicker at the ends are known as a concave lens.
  • Convex lens – The lens, which is thicker in the middle and thinner at the ends are known as a convex lens.

Stay tuned with byju’s to learn more about mirrors, concave and convex mirror and much more.


Practise This Question

In a completely dark room, can you see your face in a mirror? Why?