question_answer8) Why is a concave mirror preferred to a plane mirror for shaving?
question_answer11) Can the absolute value of refractive index of a medium be less than unity?
question_answer13) What is the cause of refraction of light?
question_answer14) Why does a ray of light bend towards normal as it passes from air to glass?
question_answer18) On what factors, does the normal shift through a refracting medium depend?
question_answer19) Does critical angle depend on colour of light? Explain.
question_answer21) An air bubble in a jar of water shines brightly. Why?
question_answer22) Why does a diamond sparkle?
question_answer23) What happens to the shining of diamond if it is dipped in a transparent oil?
question_answer27) Does refraction in a water tank make apparent depth same throughout?
question_answer29) When does a convex lens behave as a concave lens?
question_answer30) What type of a lens is an air bubble inside water? Give reason also.
question_answer33) What is lens maker's formula? Why is it so called?
question_answer35) What is the focal length and power of a rectangular glass slab?
question_answer36) Sun glasses (goggles) have curved surfaces but they do not have any power. Why?
question_answer38) Why is the power of a lens measured as the reciprocal of its focal length?
question_answer39) What happens to a focal length of a convex lens, when it is immersed in water?
question_answer51) Explain why one prefers even in summer a black umbrella to a white one?
question_answer54) Does the angle of deviation of a small-angled prism depend on angle of incidence?
question_answer59) Why does the sky appear blue? What will it look like on the moon?
question_answer60) What will be the colour of the sky in the ' absence of atmosphere?
question_answer61) Why do clouds appear white?
question_answer63) Why is yellow sodium light used for illumination in foggy conditions?
question_answer64) Why is the smoke of cigarette blue?
question_answer65) What is the cause of blue colour of ocean?
question_answer66) Explain giving reason why the sun looks reddish at sunrise and sunset.
question_answer67) Why do sometimes we observe haloes (rings) round the sun or the moon?
question_answer68) Why do we observe a spectrum in the minimum deviation position?
question_answer69) What is the difference between a spectroscope, spectrograph and spectrometer?
question_answer70) How is rainbow formed in the sky?
question_answer72) Why is the secondary rainbow fainter than the primary rainbow?
question_answer74) Why do we prefer a magnifying glass of smaller focal length?
question_answer76) The size of the moon is much smaller than stars, still it appears bigger. Why?
question_answer81) Why should the objective of a telescope have a larger focal length?
question_answer82) Why is the power of the objective of a telescope kept as small as possible?
question_answer87) Can a terrestrial telescope be used for observing astronomical objects?
question_answer94) Why should the objective of a micro- scope be of small aperture?
question_answer97) A chicken wakes up early in the morning and goes to sleep by sunset. Why?
question_answer98) Why do some people use bi-focal lenses?
question_answer101) What are real and virtual images? Distinguish between them.
question_answer110) A straight rod appears bent in water. Why?
question_answer117) Explain the twinkling of stars. Why do the planets not show twinkling effect?
question_answer120) Define focus and principal focus of a lens.
question_answer121) Distinguish between a convex lens and a concave lens.
question_answer135) A glass prism causes dispersion while a glass plate does not. Why?
question_answer136) A beam of white light on passing through a hollow prism gives no spectrum. Why?
question_answer137) Why does a parallel faced glass slab neither produce dispersion nor deviation?
question_answer138) Dispersion is caused by refraction not by reflection. Why?
question_answer139) What are the advantages of binocular vision?
question_answer140) What are the purposes of using optical instruments?
question_answer148) How is the working of a telescope different from a microscope?
question_answer149) Distinguish between a microscope and a telescope.
You need to login to perform this action.
You will be redirected in
3 sec
(b) 
Explain why any given value of \['\delta '\] corresponds to two values of angle of incidence. State the significance of point 'P' on the graph. Use this information to derive an expression for refractive index of the material of the prism. 
(i) Which one of the two lenses you will select to use as the objective lens and why? (ii) What should be the change in the distance between the lenses to have the telescope in its normal adjustment position? (iii) Calculate the magnifying power of the telescope in the normal adjustment position. 