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

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

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

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

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

• ν - ν_o

• ν

• $\sqrt{\mathrm{v} - {\mathrm{v}}_{\mathrm{o}}}$

• v_o

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?         

A vessel of height 2 d is half filled with a liquid of refractive index $\sqrt{2}$  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

• $\frac{\mathrm{n}}{\mathrm{d} \left(\mathrm{n} + \sqrt{2}\right)}$

• $\frac{\mathrm{d} \left(\mathrm{n} + \sqrt{2}\right)}{\mathrm{n} \sqrt{2}}$

• $\frac{\sqrt{2} \mathrm{n}}{\mathrm{d} \left(\mathrm{n} + \sqrt{2}\right)}$

• $\frac{\mathrm{nd}}{\mathrm{d} + \sqrt{2\mathrm{n}}}$

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)

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 A^o is/are

• none

• A only

• A and B only

• All the three metals

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?

• $\frac{\mathrm{I}}{\sqrt{3}}$

• $\sqrt{3} \mathrm{l}$

• 3 l

• $\frac{\mathrm{l}}{3}$