Test: Mirror Formulae - UPSC MCQ

Consider a plane-mirror and a fixed incident ray of light reflecting from the surface at an angle θi. Before the mirror has rotated, the angle of incidence is θ as is the angle of reflection. If the mirror is rotated through an angle φ the normal is rotated by an angle &phi and thus the angle of incidence increases to θ+φ. Therefore, the angle of reflection must also increase by φ to θ+φ The difference between the final angle of reflection and the initial angle of reflection and is 2φ.
Hence, For a fixed incident ray, the angle of the reflection is twice the angle through which the mirror has rotated: thetaf= 2φ

The correct option is B.

We know that, if the magnification value is negative sign in the concave mirror, then the image will be real and inverted. Especially, when you come to concave mirror, the images are formed at the left of the mirror. So, it forms real and inverted.

Magnification is the ratio of height of the image to the height of the object. If the image size is double of object size, then the magnification is equal to two.

Explanation:
Magnification Definition: Magnification is the ratio of the size of the image to the size of the object.
When the image is of the same size as the object:

• The size of the image will be equal to the size of the object.
• Therefore, the ratio of the size of the image to the size of the object is 1:1.
• So, the magnification is equal to one (1).

Object is always kept on the left side of the mirror therefore its distance is always negative when taken from left of pole.

Understanding the Object Distance:
The object distance, denoted by 'u', is the distance between the object and the mirror along the principal axis.
It is measured from the pole of the mirror to the object.

Sign Convention for Object Distance:
In the sign convention for spherical mirrors, distances measured in the direction of incident light are considered positive, while distances measured opposite to the incident light are considered negative.

Placement of Object on Principal Axis:
When an object is placed on the principal axis of a spherical mirror, the object distance 'u' is considered negative.
This is because the object is placed opposite to the direction of incident light, towards the left of the mirror's pole.

Conclusion:
Therefore, when an object is placed on the principal axis of a spherical mirror, the object distance 'u' is definitely negative.

Magnification is thr ratio of size of image to size of object and since it is a ratio of tel similar quantities hence it is unitless. 

Correct option is A.

The image formed by a convex mirror is always smaller in size than the object; hence its magnification is less than 1.