Spherical Mirrors
Chapter Name : Light-Reflection And Refraction |
Sub Topic Code : 101_10_10_02_05 |
Topic Name : Spherical Mirrors |
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Sub Topic Name : Mirror Formula And Magnification |
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Introduction
We can calculate the various distances like focal length, distance of object from pole, distance of image from pole by using some specific rules of sign convention.
Pre-Requisites:
Knowledge about sign convention, and image formation by spherical mirrors and plane mirrors.
Activity:
Take any mirror and see the image of an object placed at the different positions and compare the results with the results from ray diagram and comment on the nature of the sign of the various distances.
Real Life Question:
“Why the size of image formed by the plane mirror is same as the size of object?” “Why the focal length of the convex mirror is always positive?”
Key Words / FlashCards
| Key Words | Definitions (pref. in our own words) |
|---|---|
| Mirror Formula | A relation between the focal length of the mirror and the distances of object and image from the pole of the mirror. |
| Magnification | It is the ratio of height of the image to the height of the object. |
Learning aids / Gadgets
| Gadgets | How it can be used |
|---|
Real life uses :
Concave mirrors are used in headlights of cars; dentist uses this type of mirror. While convex mirror is used in making sunglasses and also used in telescopes.
Practical examples around us
| Examples | Explainations |
|---|---|
| Torches | Concave mirrors are used the torches to concentrate the light at one place. |
| Telescopes | Convex mirrors are used in the telescopes as well. |
What you learn in Theory:
Focal length of the convex mirror is always positive while focal length of the concave mirror is always negative. Distances may be negative when placed left or below to the pole of the center.
What you learn in Practice:
Positive sign in the magnification means image is virtual, what we see in the case of plane mirror and negative sign means image is real.