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31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2


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30 Questions MCQ Test Physics Class 12 | 31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2

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31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 1

The energy of a photon of wavelength λ is [1988]

Detailed Solution for 31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 1

Energy of a photon 

31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 2

The threshold frequency for photoelectric effecton sodium corresponds to a wavelength of5000 Å. Its work function is [1988]

Detailed Solution for 31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 2

W=hc/ λ
h=6.6×10-34J s
c=3×108m/s
λ =5000Å=5×10-7m
W=hc/ λ
={6.6×10-34×3×108}/(5×10-7)
=3.96×10-19J∼4x10-19J

31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 3

The de -Broglie wave corresponding to a particle of mass m and velocity v has a wavelength associated with it [1989]

Detailed Solution for 31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 3

De-Broglie wavelength 

31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 4

Energy levels A, B, C of a certain atom correspond to increasing values of energy i.e., EA < EB < EC. If λ1, λ2, λ3 are the wavelengths of radiation corresponding to the transitions C to B, B to A and C to A respectively, which of the following relation is correct? [1990, 2005]

Detailed Solution for 31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 4

Now,
(EC - EA) = (EC - EB ) + (EB - EA

)

31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 5

A radio transmitter operates at a freqency 880kHz and a power of 10 kW. The number ofphotons emitted per second is [1990]

Detailed Solution for 31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 5

No. of photons emitted per sec,

31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 6

The momentum of a photon of an electromagneticradiation is 3.3 × 10–29 kgms–1. What is thefrequency of the associated waves ? [h = 6.6 × 10–34 Js; c = 3 × 108 ms–1)            [1990]

Detailed Solution for 31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 6

p=3.3×10−29 kgms−1
λ=h/mv
c/v=h/p​
v=pc/h​
=(3.3×10−29×3×108​)/(6.6×10−34)
=1.5×1013Hz
So, the answer is option (D).
 

31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 7

Consider an electron in the nth orbit of ahydrogen atom in the Bohr model. Thecircumference of the orbit can be expressed interms of de-Broglie wavelength λ of that electronas [1990]

Detailed Solution for 31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 7

The circumference of an orbit in an atom in
terms of wavelength of wave associated with
electron is given by the relation,
circumference = nλ
where, n = 1, 2, 3, .......

31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 8

The wavelength of a 1 keV photon is 1.24 × 10–9 m. What is the frequency of 1 MeV photon ? [1991]

Detailed Solution for 31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 8

Here, hc/λ  = 103 eV and hv = 106 eV

31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 9

Photoelectric work function of a metal is 1eV.Light of wavelength λ�� = 3000 Å falls on it. Thephoto electrons come out with velocity [1991]

Detailed Solution for 31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 9

Solving we get, v ≌ 106 m/s

31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 10

The cathode of a photoelectric cell is changedsuch that the work function changes from W1 toW2 (W2 > W1). If the current before and afterchanges are I1 and I2, all other conditionsremaining unchanged, then (assuming hν > W2)[1992]

Detailed Solution for 31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 10

The work function has no effect on
photoelectric current so long as hv > W0.
The photoelectric current is proportional to
the intensity of incident light. Since there is
no change in the intensity of light, hence I1
= I2.

31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 11

An ionization chamber with parallel conductingplates as anode and cathode has 5 × 107 electronsand the same number of singly charged positiveions per cm3. The electrons are moving towards the anode with velocity 0.4 m/s. The currentdensity from anode to cathode is 4μA/m2. Thevelocity of positive ions moving towardscathode is     [1992]

Detailed Solution for 31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 11

Current = Ie+ Ip
Ie and Ip are current due to electrons and
positively charged ions.
I = neAVd

Given, I / A = 4 x10-6 A/ m2

4x10-6 x A = 5 x10-6 x1.6 x A(v + 0.4)

31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 12

When light of wavelength 300 nm (nanometer) falls on a photoelectric emitter, photoelectronsare liberated. For another emitter, however, light of 600 nm wavelength is sufficient for creatingphotoemission. What is the ratio of the work functions of the two emitters?  [1993]

Detailed Solution for 31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 12

Work function   ϕ=hc​/λ
⟹ ϕ12​ ​​=​λ2​​/λ1
Given :  λ1​=300 nm          λ2​=600 nm
∴  ​ϕ1/ ϕ2 ​​=600/300 ​=2

31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 13

Number of ejected photoelectron increases withincrease    [1993]

Detailed Solution for 31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 13

Photoelectric current is directly proportional
to the intensity of incident light.

31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 14

Momentum of a photon of wavelength λ is

Detailed Solution for 31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 14

According to de Brogie wave equation,

31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 15

In photoelectric effect the work function of ametal is 3.5 eV. The emitted electrons can bestopped by applying a potential of –1.2 V. Then[1994]

Detailed Solution for 31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 15

hv = W0 + Ek = 3.5 + 1.2 = 4.7 eV

31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 16

Doubly ionised helium atoms and hydrogen ions are accelerated from rest through the same potential drop. The ratio of the final velocities of the helium and the hydrogen ion is [1994]

Detailed Solution for 31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 16

Answer :- d

Solution :- Ionised atoms = Helium (Given)

Ionised ions = Hydrogen (Given)

Potential difference = constant (Given)

Thus, mv² = eV, or

V = (2eV/m)1/2

The mass of helium ion is four times than that of hydrogen ion.

Therefore, the charge on helium ion is twice that of hydrogen ion.

vHe/vH = √2

Thus, The ratio of final velocities of helium and hydrogen is √2:1

31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 17

Gases begin to conduct electricity at low pressurebecause [1994]

Detailed Solution for 31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 17

The ionisation requires high energy
electrons.

31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 18

Kinetic energy of an electron, which isaccelerated in a potential difference of 100 V is[1995]

Detailed Solution for 31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 18

Potential difference (V) = 100 V. The kinetic
energy of an electron = 1 eV = 1 × (1.6 × 10–19)
= 1.6 × 10–19 J. Therefore kinetic energy in
100 volts = (1.6 × 10–19) × 100 = 1.6 × 10–17J.
[Alt : K.E. = qV
= 1.6 × 10–19 × 100 J = 1.6 × 10–17]

31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 19

The wavelength associated with an electron,accelerated through a potential difference of 100V, is of the order of [1996]

Detailed Solution for 31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 19

Potential difference = 100 V
K.E. acquired by electron = e (100)

According to de Broglie's concept

31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 20

An electron of mass m and charge e is accelerated from rest through a potential difference of V volt in vacuum. Its final speed will be [1996]

Detailed Solution for 31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 20

Kinetic energy of electron accelerated
through a potential V= eV

31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 21

Which of the following statement is correct?   [1997]

Detailed Solution for 31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 21

According to photoelectric effect, speed of
electron (kinetic energy) emitted depends
upon frequency of incident light while
number of photoelectrons emitted depends
upon intensity of incident light. Hence, as
the intensity of light increases, the
photocurrent increases. In a photo-cell, the
photocurrent has no relation with the applied
voltage.
Stopping potential is the (negative) potential
at which the current is just reduced to zero.
It is independent of intensity of light but
depends on the frequency of light similar to
K.E.

31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 22

Cosmic rays are [1997]

Detailed Solution for 31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 22

Cosmic rays have low wavelength and high
frequency hence these rays emit high energy
radiation.

31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 23

The X-rays cannot be diffracted by means of anordinary grating because of         [1997]

Detailed Solution for 31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 23

We know that the X-rays are of short
wavelength as compared to grating constant
of optical grating. As a result of this, it makes
difficult to observe X-rays diffraction with
ordinary grating.

31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 24

In a photo-emissive cell, with exciting wavelength λ, the fastest electron has speed v. If the exciting wavelength is changed to  the speed of the fastest emitted electron will be [1998]

Detailed Solution for 31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 24

31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 25

The 21 cm radio wave emitted by hydrogen ininterstellar space is due to the interaction called the hyperfine interaction in atomic hydrogen.The energy of the emitted wave is nearly       [1998]

Detailed Solution for 31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 25

E=hc/λ​=6.6×10−34×3×108​/21×10−2 =0.94×10−24≈10−24J

31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 26

Light of wavelength 5000 Å falls on a sensitiveplate with photo-electric work function of 1.9 eV.The kinetic energy of the photo-electronsemitted will be [1998]

Detailed Solution for 31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 26

From photoelectric equation
KE=hc/λ​−W
(6.6×10−34×3×108/5000×10−10)−(1.9×1.6×10−19)
=0.58eV

31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 27

As the intensity of incident light increases        [1999]

Detailed Solution for 31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 27

K.E. of electrons emitted depends upon the
frequency of incident rays rather than the
intensity. While number of photo electrons
emitted depends upon intensity of radiation.

31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 28

The photoelectric work function for a metalsurface is 4.125 eV. The cut off wavelength forthis surface is [1999]

Detailed Solution for 31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 28

Let λ0 be cut off wavelength.

31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 29

Einstein work on the photoelectric effect provided support for the equation          [2000]

Detailed Solution for 31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 29

Einstein work on photoelectric effect
supports the equation E = hv.It is based on
quantum theory of light.

31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 30

Which of the following moving particles (movingwith same velocity) has largest wavelength ofmatter waves? [2002]

Detailed Solution for 31 Year NEET Previous Year Questions: Dual Nature of Radiation & Matter - 2 - Question 30

de-Broglie wavelength 

For same velocity,  

Out of given particles, the mass of electron
is minimum, so the associated de-Broglie
wavelength is maximum for electron.

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