A leaf which contains only green pigments, is illuminated by

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121.

A leaf which contains only green pigments, is illuminated by a laser light of wavelength 6328 pm. It would appear to be

  • brown

  • black

  • red

  • green


B.

black

If an object reflects the colour of light incident on it, it will appear with that colour but if object absorbs the colour of light, it will appear to be black. since the given wavelength does not belong to green, so it will be absorbed by the leaf and hence, it would appear to be black.


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122.

Flash light equipped with a new set of batteries, produces bright white light. As the batteries wear out

  • the light intensity gets reduced with no change in its colour

  • light colour changes first to yellow and then red with no change in intensity

  • it stops working suddenly while giving white light

  • colour changes to red and also intensity gets reduced


123.

If alpha, beta and gamma rays carry same momentum, which has the longest wavelength?

  • Alpha rays

  • Beta rays

  • Gamma rays

  • None all have same wavelength


124.

The kinetic energy of an electron, which is accelerated in the potential difference of 100 V, is

  • 1.6 × 10-17 J

  • 1.6 × 10-14 J

  • 1.6 × 10-10 J

  • 1.6 × 10-8 J


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125.

Light of frequency v falls on material of threshold frequency vo, Maximum kinetic energy of emitted electron is proportional to 

  • ν - νo

  • ν

  • v - vo

  • vo


126.

Which one of the following graph represents the variation of maximum kinetic energy (Ek) of the emitted electrons with frequency v in photoelectric effect correctly?         

                 


127.

A vessel of height 2 d is half filled with a liquid of refractive index 2  and the other half with a liquid of refractive index n (the given liquids are immiscible). Then, the apparent depth of the inner surface of the bottom of the vessel (neglecting the thickness of the bottom of the vessel) will be

  • nd n + 2

  • d n + 2n 2

  • 2 nd n + 2

  • ndd + 2n


128.

Light travels faster in air than that in glass. This is accordance with

  • wave theory of light

  • corpuscular theory of light

  • neigther (a) nor (b)

  • Both (a) and (b)


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129.

The work function for metals A, Band C are respectively 1.92  eV,  2.0 eV and 5 eV. According to Einstein's equation the metals which will emit photo, electrons for a radiation of wavelength 4100 Ao is/are

  • none

  • A only

  • A and B only

  • All the three metals


130.

If the sun rays are incidenting at 60° angle and intensity is I. If the sun rays are made incident at 30° angle, then what will be the intensity?

  • I3

  • 3 l

  • 3 l

  • l3


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