Dual Nature of Radiation and Matter Practice Questions - DPP for JEE

 Page 1


PART-I (Single Correct MCQs)
1. Two identical photocathodes receive light of frequencies f
1
 and f
2
. If the
velocites of the photo electrons (of mass m ) coming out are
respectively v
1
 and v
2
, then
(a)
(b)
(c)
(d)
2. The anode voltage of a photocell is kept fixed. The wavelength ? of the
light falling on the cathode is gradually changed. The plate current I of
Page 2


PART-I (Single Correct MCQs)
1. Two identical photocathodes receive light of frequencies f
1
 and f
2
. If the
velocites of the photo electrons (of mass m ) coming out are
respectively v
1
 and v
2
, then
(a)
(b)
(c)
(d)
2. The anode voltage of a photocell is kept fixed. The wavelength ? of the
light falling on the cathode is gradually changed. The plate current I of
the photocell varies as follows
(a)
(b)
(c)
(d)
3. In a photoelectric experiment, with light of wavelength ?, the fastest
electron has speed v. If the exciting wavelength is changed to 5?/4, the
speed of the fastest emitted electron will become
(a)
(b)
(c) less than 
(d) greater than 
4. The wavelength ?
e
 of an electron and ?
p
 of a photon are of same energy
E are related by
(a)
Page 3


PART-I (Single Correct MCQs)
1. Two identical photocathodes receive light of frequencies f
1
 and f
2
. If the
velocites of the photo electrons (of mass m ) coming out are
respectively v
1
 and v
2
, then
(a)
(b)
(c)
(d)
2. The anode voltage of a photocell is kept fixed. The wavelength ? of the
light falling on the cathode is gradually changed. The plate current I of
the photocell varies as follows
(a)
(b)
(c)
(d)
3. In a photoelectric experiment, with light of wavelength ?, the fastest
electron has speed v. If the exciting wavelength is changed to 5?/4, the
speed of the fastest emitted electron will become
(a)
(b)
(c) less than 
(d) greater than 
4. The wavelength ?
e
 of an electron and ?
p
 of a photon are of same energy
E are related by
(a)
(b)
(c)
(d)
5. The cathode of a photoelectric cell is changed such that the work
function changes from W
1
 to W
2
 (W
2
 > W
1
). If  the current before and
after changes are I
1
 and I
2
, all other conditions remaining unchanged,
then (assuming h? > W
2
)
(a) I
1
 = I
2
(b) I
1
 < I
2
(c) I
1
 > I
2
(d) I
1
 < I
2
 <  2 I
1
6. The maximum velocity of an electron emitted by light of wavelength ?
incident on the surface of a metal of work-function f is
(a)
(b)
(c)
(d)
7. Which one of the following graphs represents the variation of maximum
kinetic energy (E
K
) of the emitted electrons with frequency ? in
photoelectric effect correctly ?
(a)
Page 4


PART-I (Single Correct MCQs)
1. Two identical photocathodes receive light of frequencies f
1
 and f
2
. If the
velocites of the photo electrons (of mass m ) coming out are
respectively v
1
 and v
2
, then
(a)
(b)
(c)
(d)
2. The anode voltage of a photocell is kept fixed. The wavelength ? of the
light falling on the cathode is gradually changed. The plate current I of
the photocell varies as follows
(a)
(b)
(c)
(d)
3. In a photoelectric experiment, with light of wavelength ?, the fastest
electron has speed v. If the exciting wavelength is changed to 5?/4, the
speed of the fastest emitted electron will become
(a)
(b)
(c) less than 
(d) greater than 
4. The wavelength ?
e
 of an electron and ?
p
 of a photon are of same energy
E are related by
(a)
(b)
(c)
(d)
5. The cathode of a photoelectric cell is changed such that the work
function changes from W
1
 to W
2
 (W
2
 > W
1
). If  the current before and
after changes are I
1
 and I
2
, all other conditions remaining unchanged,
then (assuming h? > W
2
)
(a) I
1
 = I
2
(b) I
1
 < I
2
(c) I
1
 > I
2
(d) I
1
 < I
2
 <  2 I
1
6. The maximum velocity of an electron emitted by light of wavelength ?
incident on the surface of a metal of work-function f is
(a)
(b)
(c)
(d)
7. Which one of the following graphs represents the variation of maximum
kinetic energy (E
K
) of the emitted electrons with frequency ? in
photoelectric effect correctly ?
(a)
(b)
(c)
(d)
8. If E
1
, E
2
, E
3
 are the respective kinetic energies of an electron, an alpha-
particle and a proton, each having the same de-Broglie wavelength, then
(a) E
1 
> E
3 
> E
2
(b) E
2 
> E
3 
> E
1
(c) E
1 
> E
2 
> E
3
(d) E
1 
= E
2 
= E
3
9. In photoelectric effect, stopping potential for a light of frequency n
1
 is
V
1
. If light is replaced by another having a frequency n
2
 then its
stopping potential will be
(a)
(b)
(c)
Page 5


PART-I (Single Correct MCQs)
1. Two identical photocathodes receive light of frequencies f
1
 and f
2
. If the
velocites of the photo electrons (of mass m ) coming out are
respectively v
1
 and v
2
, then
(a)
(b)
(c)
(d)
2. The anode voltage of a photocell is kept fixed. The wavelength ? of the
light falling on the cathode is gradually changed. The plate current I of
the photocell varies as follows
(a)
(b)
(c)
(d)
3. In a photoelectric experiment, with light of wavelength ?, the fastest
electron has speed v. If the exciting wavelength is changed to 5?/4, the
speed of the fastest emitted electron will become
(a)
(b)
(c) less than 
(d) greater than 
4. The wavelength ?
e
 of an electron and ?
p
 of a photon are of same energy
E are related by
(a)
(b)
(c)
(d)
5. The cathode of a photoelectric cell is changed such that the work
function changes from W
1
 to W
2
 (W
2
 > W
1
). If  the current before and
after changes are I
1
 and I
2
, all other conditions remaining unchanged,
then (assuming h? > W
2
)
(a) I
1
 = I
2
(b) I
1
 < I
2
(c) I
1
 > I
2
(d) I
1
 < I
2
 <  2 I
1
6. The maximum velocity of an electron emitted by light of wavelength ?
incident on the surface of a metal of work-function f is
(a)
(b)
(c)
(d)
7. Which one of the following graphs represents the variation of maximum
kinetic energy (E
K
) of the emitted electrons with frequency ? in
photoelectric effect correctly ?
(a)
(b)
(c)
(d)
8. If E
1
, E
2
, E
3
 are the respective kinetic energies of an electron, an alpha-
particle and a proton, each having the same de-Broglie wavelength, then
(a) E
1 
> E
3 
> E
2
(b) E
2 
> E
3 
> E
1
(c) E
1 
> E
2 
> E
3
(d) E
1 
= E
2 
= E
3
9. In photoelectric effect, stopping potential for a light of frequency n
1
 is
V
1
. If light is replaced by another having a frequency n
2
 then its
stopping potential will be
(a)
(b)
(c)
(d)
10. A certain metallic surface is illuminated with monochromatic light of
wavelength ?. The stopping potential for photo-electric current for this
light is 3V
0
. If the same surface is illuminated with light of wavelength
2?, the stopping potential is V
0
. The threshold wavelength for this
surface for photo-electric effect is
(a) 4 ?
(b)
(c)
(d) 6 ?
11. The ratio of the respective de Broglie wavelengths associated with
electrons accelerated from rest with the voltages 100 V, 200 V and 300
V is
(a) 1 : 2 : 3
(b) 1 : 4 : 9
(c)
(d)
12. Two radiations of photons energies 1 eV and 2.5 eV, successively
illuminate a photosensitive metallic surface of work function 0.5 eV.
The ratio of the maximum speeds of the emitted electrons is :
(a) 1 : 4
(b) 1 : 2
(c) 1 : 1
(d) 1 : 5
13. Photoelectric emission is observed from a metallic surface for
frequencies v
1
 and v
2
 of the incident light rays (v
1
 > v
2
).  If the
maximum values of kinetic energy of the photoelectrons emitted in the