UPSC General Science :Wave and Optics Notes Part 2

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Today’s Topic : Wave and Optics

Q1. When an eye fails to see vertical and horizontal lines equally distinctly, it is said to be a suffering from which one of the following:

a) Presbyopia

b) Adermatoglyphia

c) Flatter lens

d) Astigmatism.

Ans:     D

Explanation:    When the person suffering from astigmatism, rays of light from the horizontal and vertical lines in a plane are not focussed in the same plane on the image. This defect is caused when the curvature of the cornea becomes different in different axial plane. This defect is corrected by using the spectacles with cylindrical lenses.

Q2. In the making of leather, which of the following is involved in the process of tanning:

a) Lubrication and aesthetic appeal.

B) Finishing to obtain proper thickness.

C) Displacement of water and combination with fibrous protein, cllegn.

D) Removal of hair, flesh and rat.

Ans:    C

Explanation:    The making of leather is involve in the process of tanning is displacement of water and combination with fibrous, protein and collegn. Tanning increasing resistance to heat and decomposition caused by water and mciro organism. So option (c) is correct.

Q3. Total internal reflection occur when light passes from:

a) Rarer to denser

b) Denser to rarer

c) It occurs irrespective of medium

d) It is same as refraction

Ans:     B

Explanation:    TIR occurs when light passes from denser to rarer medium and angle of incidence < i is more than critical angle <ic. Through this condition light does not pass to another medium. In optical fibre communication TIR principle is used. It has greater use in medical science like endoscopy. If <i> Iic then 100% reflection occurs.

Q4. Which one of the following is used in fingerprints on a piece of paper:

a) b-rays

b) Ultraviolet radiation

c) Gamma-rays

d) X-rays.

Ans:     B

Explanation:    The ultraviolet radiation is used in finger print of any object/person on a piece of paper. Finger print on a  piece of paper may be detected by sprinkling fluorescence power and then examining it in the ultra violet radiation/light.

Q5. Which of the following is true about total reflection of prism:

a) One angle of prism is 180° and other two are of 0 each.

b) Each angle of prism is of 60°.

c) One angle of prism is 90° and other two are of 45°.

d) One angle of prism is 80° and other two are of 50° each.

Ans:     C

Explanation:    About the total reflection of prism one angle are 45° each. The total reflection are used in optical interments such as microscope, telescope, spectroscope, prism binoculars etc.

Q6. Consider the following statements and select the correct code: Which of the following is/are not a property of Infrared spectrum:

1) They have large wavelength.

2) They eject electrons from metals on which they falls.

3) They show heating effect.

4) They are observed by the glass but not by rock salt.


a) 1 and 4

b) Only 2

c) 2 and 3

d) 1, 2, 3 and 4

Ans:     B

Explanation:    Except code (b) all are property of infrared spectrum. The eject electrons from metal on which they fall is not property of infrared spectrum because it is property of ultraviolet radiation.

Q7. The angle of incidence for which the angle of refraction is equal to 90 is know as critical angle.

Which of the following has largest critical angle:

a) Glycerine

b) Diamond

c) Water

d) Crown glass.

Ans:     C

Explanation:    Critical angle of crown glass is 41°.25’, Critical angle of water is 48°.5’ Critical angle of diamond is 42°.25’ Critical angle of glycerine is 44°.30’. Critical angle of paraffin is 44°.12’.

Q8. Which one of the following concave mirror is not used:

a) Rear-view mirror

b) Reflector in search light

c) Dental used

d) None of these.

Ans:     A

Explanation:    The concave mirror is not used in rear-view mirror. The convex mirror used in rear – view mirror. It is also used in street lamps as a reflector to diverge the light over a large surface. Reflector of search light dental used of the concave mirror.

Q9. Which one of the following instruments is used in a trench to view what is the happening out side:

a) Spectrometer

b) Clino state

c) Simple periscope

d) None of these.

Ans:    C

Explanation:    The simple periscope to used to witness the game by a person sitting in back row over the heads of the observer can seen weather a ship is coming while lying in deep sea. It is consist a long tube with opening at the top and the bottom and two plane mirror fixed at an angle 45° to this axis of the tube such that the mirror are parallel to each other.

Q10. Ear of a beat is an example of which one of the following options:

a) Lever of the fourth order

b) Lever of the fifth order

c) Lever of the second order

d) None of these.

Ans:    C

Explanation:    Ear of a beat is an example of lever of the second order. In lever of second order, lead is situated between effort and fulcrum. Nut, cracker, wheel borrow, ear of a bet, etc. Are lever of the second order.