Difficult Questions

## Ray Optics And Optical Instruments

- Are you well prepared? Practice hard questions to be more confident about the chapter
1
The apparent depth of an object through layers of multiple media depends upon the refractive indices of the media and their thickness. Figure out the situation with a real world problem.
A fish looking up through the water sees the outside world contained in a circular horizon. If the refractive index of water is and the fish is below the surface, the radius of this circle in cm is _____.
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2
A beam of light rays refracts when it passes through different mediums having different refractive indices.
Refraction, critical angle and total internal reflection come into picture. Let's see the problem
A layer of oil of refractive index floats on water of refractive index . A beam of light is directed upward from a source in the water. Show that the critical angle for a total internal reflection is independent of , even though, for angles close to C (critical angle), the total internal reflection always takes place at the oil-air surface.
3
Total internal reflection occurs when the light rays travel from a more dense medium into a less dense medium (i.e. glass to air) and also the angle of incidence must be greater than the critical angle. Let's solve a question and learn how it works.
An optical fibre has a cylindrical cross-section of diameter and index of refraction bent sharply. What is the smallest radius of curvature at a short bent section for which the total internal reflection will be assured for light initially travelling parallel to the axis of the fibre?
4
When light rays pass through combination of prisms and mirrors, it get reflect and refract simultaneously. Multiple images are formed in this case. Let's see how it works.
is a point object kept on the principal axis of a concave mirror of radius of curvature . is a prism of angle . Light falling on the prism (at small angle of incidence) gets refracted through the prism and then falls on the mirror. Refractive index of the prism is . Find the distance between the images formed by the concave mirror due to this light.
5
When we place an object in front of a compound microscope a linear, angular and total magnification produced by a compound microscope. Try to understand this with a problem.
The magnifying power of a compound microscope is and the distance between its two lenses is when the final image is at the near point of the eye. If the focal length of eyepiece is , the focal length of objective is :
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6
When we see an object with the help of telescope its magnified and resolved image is seen by us. It is completely depends upon the resolving power of the telescope. Let's see a problem and learn how it works.
A telescope has an objective lens of focal length 150 cm and an eyepiece of focal length 5 cm. If a 50 m tall tower at a distance of 1 km is observed through this telescope in normal setting, the angle formed by the image of the tower is , then close to.
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