light

A point object is placed at a distance of 20 cm from a convex mirror of focal length 20 cm. The image will form at:

• at infinity

• at focus

• at the pole

• behind the mirror

If the power of a lens is – 2 D, what is its focal length?

• +50 cm

• -100 cm

• -50 cm

• +100 cm

If the magnification produced by a lens has a negative value, the image will be

• virtual and inverted

• virtual and erect

• real and erect

• real and inverted

A ray of light is travelling from a rarer medium to a denser medium. While entering the denser medium at the point of incidence, it

• goes straight into the second medium

• bends towards the normal

• bends towards the normal

• does not enter at all

The angle of incidence for a ray of light having zero reflection angle is

An object at a distance of 30 cm from a
concave mirror gets its image at the same point. The focal length of the mirror is

A concave mirror of focal length 20 cm forms an image having twice the size of object. For the virtual position of object, the position of object will be at

The image formed by concave mirror is real, inverted and of the same size as that of the object. The position of object should be

• at the focus

• at the centre of curvature

• between focus and centre of curvature

• beyond centre of curvature

If a man’s face is 25 cm in front of concave shaving mirror producing erect image 1.5 times the size of face, focal length of the mirror would be

The refractive index of water is 1.33. The speed of light in water will be

• 1.33 × 10⁸ m/s

• 3 × 10⁸ m/s

• 2.26 × 10⁸ m/s

• 2.66 × 10⁸ m/s