Spherical Mirrors -2 Friday, 10 July 2020Spherical Mirrors - 2

Image formation

In order to determine the image , we take at least two incident rays and draw their reflected rays. The image is formed where two rays meet or appear to come from in case of the convex mirror.

Concave Mirrors

Case I - When the object is at infinity

Note that we use a straight vertical line to represent the mirror.

Characteristics of the image :

•real

•diminished

•formed in front of the mirror

•inverted

Case II- When the object is beyond C

Characteristics of the image

•real

•diminished

•formed in front of mirror

•inverted

Case III- When the object is at C

Characteristics of the image

•real

•same size as object

•formed in front of mirror

•inverted

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Spherical Mirrors -2 Friday, 10 July 2020Case IV- When the object is between C and F

Characteristics of the Image

Image is

•real

•magnified

•formed in front of mirror

•inverted

Case V- When the object is at F

Characteristics of the Image

Image is

•real

•highly magnified

•formed in front of the mirror

•inverted

Case VI- When the object is between F and P

Characteristics of the Image

Image is

•virtual

•magnified

•formed behind the mirror

•upright

Note : The above shows when an object is close to the mirror an upright , magnified image is formed. For this reason the concave mirror can be used as a makeup or shaving mirror.

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Spherical Mirrors -2 Friday, 10 July 2020Convex Mirror

For all positions of the object the ray diagram for obtaining the image is the same.

Characteristics of the Image

Image is

•virtual

•diminished

•formed behind the mirror

•upright

Note : Since a convex mirror forms upright and diminished image for all positions of the object , it is used as a rear view mirror in cars. The entire view at the rear (back) of the car can be accommodated in a small mirror. We say that the convex mirror has a wide field of view.

Uses of Spherical Mirror

Concave mirrors

• Shaving and makeup mirror ( diagram shown above)

• Headlight mirror of vehicles

A concave reflector in a car headlight

• Telescopes Concave mirrors are used in microscopes to collect light from a lamp, shining it up onto a slide containing a specimen so it can be viewed through a magnification lens.

• Microscopes Similar to how a concave mirror works in a microscope, the concave mirror in the telescope collects light.

Convex Mirrors

3 Mr P. Moktan, SAS

Spherical Mirrors -2 Friday, 10 July 2020Used as rear view mirror in vehicles ( ray diagram is given above ).

This is the mirror that is placed in a bend on a road or ahead of a tunnel, in an ATM etc. The purpose is the same - to provide a wide field of view of what is behind.

Used in magnifying glasses Convex mirrors are widely used for making magnifying glasses. In order to make a magnifying glass, two convex mirrors are placed back to back.

Used in sunglasses

Note : Remember the magnifying glass and rear view mirror with reasons. Next we will be doing some exercises on the lesson.

4 Mr P. Moktan, SAS