UPSC General Science :Wave and Optics Notes Part 1

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Today’s Topic : Wave and Optics

Q1. A type of wave disturbance in which wave particle vibrates along the direction of wave movement is known as:

a) Stationary wave

b) Progressive wave

c) Electromagnetic wave

d) Longitudinal wave.

Ans:     D

Explanation:    Wave is a disturbance. It has energy and momentum and propagates from one point to another point. It has certain frequency and wavelength. It is of two types

1) Transverse waves

2) Longitudinal waves.

Transverse wave – Medium particle vibrates perpendicular to the direction of propagation of wave. Longitudinal wave – Medium particle vibrates along the direction of wave movement.

Q2. Match the following List-1 and List-2:

List-1 (Indian Physicists)                     List-2: (Contribution)

  1. S.N. Bose                                     A. Evolution of stars
  2. C.V. Raman                                  B. Quanthem statistics
  3. S. Chandrashekhar                      C. Cosmic radiation
  4. H.J. Bhabha.                                D. Inelastic scattering of light by molecules.


A         B          C          D

a) 3         1          4          2

b) 1         2          3          4

c) 1         3          2          4

d) 3         1          2          4

Ans:     A


S.N.Bose                     –           Quanthem statistics

C.V.Raman                  –           Inelastic scattering of light by molecules

H.J.bhabha                  –           Cosmic radiation

S.Chandrashekhar       –           Evolution of stars.

Q3. Hepatitis ‘B’ vaccine is categorised as:

a) Interferon

b) Second generation vaccine

c) First generation vaccine

d) Third generation vaccine

Ans:     B

Explanation:    First generation vaccines produced by conventional technique. It’s success rate is low and not safer. Second generation vaccines are better and safer vaccine, they consists of a few antigens present on the surface of the infecting agents rather than whole inactivated organism. Hepatitis ‘B’ is caused by virus. In this disease liver is affected. One of the main cause of Hepatitis ‘B’ is contaminated water.

Q4. Which of the following statements is correct:

a) Wave velocity is the product of wavelength and frequency.

b) The sharpness of a musinal tone depends on its pitch.

c) Wavelength of sound wave is inversely related to frequency.

d) Wave energy depends on frequency of the wave.

a) a and b

b) b and c

c) a, b and c

d) All of the above.

Ans:     D


Wave velocity (C) = Wavelength x frequency

C =  x v

λ =

Wave frequency is inversely related to wavelength i.e. frequency increae wavelength decreases.

The sharpness of a musical tone depends on its pitch. More the pitch (frequency), more will be sharpness. Energy of wave (E) = hv

v = frequency

h = Plack’s constant

h = 6.67 x10-34 J – sec.

Q5. Automatic door open are usually trigered by sensor which sense the presence of a person near the door. These sensor sense which of the following to activate the opening of the door:

a) Pressure

b) Interruption of a beam of visible infrared light

c) Change in the magnetic field

d) a and b

Ans:    D

Explanation:    Basically two types of sensor, which either sense pressure or interruption of a beam of visible or infrared light. In the beam sensor type door opener the source of the beam and the detector are placed opposite to each other in the passage ways in front of the door in a such way that the beam crosses the passage ways. If the sensor is of pressure type it is placed below a movable platform in front of the door.

Q6. Match the List-1 to List-2 and select the correct code:

List-1:                                                  List-2:

  1. Magnifying glass                               1. Two convex lense
  2. Galilian telescope                              2. Three convex lense
  3. Compound microscope                     3. A convex lense and concave lense
  4. Terrestrial telescope.                         4. Double convex lenses.


A         B          C          D

a) 1         2          3          4

b) 4         3          1          2

c) 3         2          4          1

d) 1         4          3          2

Ans      B


Magnifying glass                      –           Double convex lense,

Galilian telescope                    –           A convex and a concave lense,

Compound microscope           –           Three convex lense.

Q7. Rain sensor fitted on the windshield wiper of some automobiles are based on the principle:

a) Heat radiation

b) Total internal reflection

c) Surface tension

d) All of the above.

Ans:    B

Explanation:    Rain sensor fitted on windshield wiper of automobiles are based on total internal reflection. This case of infrared light/spectrum falls onto windshield from the inside of the automobile when the drop of water appear on the glass, the reflected light is less. On sensing this the wiper on the windshield start functioning.

Q8. When a pigments are mixed, each one absorb certain colours or each one subs tract from white light and resulting colour is depend on the light waves that are not absorbs. Primary pigments are the complements of three primary colours. Consider the following statement and select correct code:

1) When three primary pigments are mixed, we get the black colour.

2) Cyan is the complement of green, magenta the complements of blue and yellow the complements of red.

a) Only 2 is correct

b) Only 1 is correct

c) 1 and 2 both are correct

d) Both are false.

Ans:     B

Explanation:    The cyan is the complements of red, magenta is the complement of green and yellow is the complements of blue. When three primary colours/pigments (cyan, magenta and yellow) are mixed in proper proportion all the colours are subtract from white light and his mixture is black.

Q9. The surface temperature of which of the following planets according to latest researches is higher than that of any other plants and hotter than most ovens:

a) Mercury

b) Pluto

c) Uranus

d) Venus

Ans:     D

Explanation:    The surface temperature of venus planet is about 462C. The sun’s radiations energy filter into the planets atmosphere. The large droplet of sulfuric acid (H2SO4) is present venus cloud and the great quantity of CO2 in the atmosphere seem to trap of solar energy of the planets surface.

Q10. Consider the following statements and select the correct code:

1) The near point of human eyes decreases with age.

2) Presbyopia is caused due to ageing when it becomes very difficult to change the lense of curvature.

a) Only 2 is correct

b) Both 1 and 2 are correct

c) Only 1 is correct

d) Both 1 and 2 are incorrect

Ans:     A

Explanation:    A standard near point distance of 25cm is typically assumed in the design of optional instruments and characterizing optical devised such a magnifying glasses. Without correction, the near point is 3 inches (7cm) at age of 10, 6 inches (16cm) at age of 40 to 39 inches (1 meter) at age of 60. As a result a 60 year old must use corrective lense to read books. Presbyopia is a caused in the advance stage when muscle become flexible.

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