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NEET UG PHYSICS MCQ: RAY OPTICS

1 Medium

1 of 1

Application +4 | -1

Two thin lenses, one of focal length

+ \,60\,\,cm

and the other of focal length

- \,20\,\,cm

are put in contact. The combined focal length is

View answer and explanation

Correct option: D

- \,30\,\,cm

Option D (

\ - \,30\,\,cm

) is correct because it is calculated using the formula for the combined focal length of two lenses in contact.

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An object 5 cm tall is placed

\mathrm{1}\,\,\mathrm{m}

from a concave spherical mirror which has a radius of curvature of

\mathrm{20}\,\,\,\mathrm{cm}

. The size of the image is Red colour is used for danger signals because A ray of light is incident on the hypotenuse of a right-angled prism after travelling parallel to the base inside the prism. If

\mathrm{\mu }

is the refractive index of the material of the prism, the maximum value of the base angle for which light is totally reflected from the hypotenuse is Statement-A: The minimum distance between an object and its real image formed by a convex lens is

2{f}

.

Statement-B: The distance between an object and its real image is minimum when its magnification is -1. Assertion: We cannot produce a real image by plane or convex mirrors under any circumstances.
Reason: The focal length of a convex mirror is always taken negative. If both the object and image are at infinite distance from a refracting telescope its magnifying power will be equal to