DPP-25
Q.1 In photoelectric effect, stopping potential depends on
(A) frequency of the incident light (B) intensity of the incident light by varies source distance
(C) emitter’s properties (D) frequency and intensity of the incident light
Q.2 An electron in hydrogen atom first jumps from second excited state to first excited state and then, from
first excited state to ground state. Let the ratio of wavelength, momentum and energy of photons in the
two cases be x, y and z, then select the wrong answer/(s) :
(A) z = 1/x (B) x=9/4 (C) y=5/27 (D) z=5/27
Q.3 An electron is in an excited state in hydrogen-like atom. It has a total energy of –3.4 eV. If the kinetic
energy of the electron is E and its de-Broglie wavelength is , then
(A) E = 6.8 eV, = 6.6 × 10–10 m (B) E = 3.4 eV, = 6.6 × 10–10 m
(C) E = 3.4 eV, = 6.6 × 10 m –11 (D) E = 6.8 eV, = 6.6 × 10–11 m
Q.4 A particular hydrogen like atom has its ground state binding “energy 122.4eV. Its is in ground state.
Then:
(A) Its atomic number is 3
(B) An electron of 90eV can excite it.
(C) An electron of kinetic energy nearly 91.8eV can be brought to almost rest by this atom.
(D) An electron of kinetic energy 2.6eV may emerge from the atom when electron of kinetic energy
125eV collides with this atom.
Q.5 A beam ofultraviolet light of all wavelengths passes through hydrogen gas at room temperature, in the
x-direction. Assume that all photons emitted due to electron transition inside the gas emerge in the
y-direction. Let A and B denote the lights emerging from the gas in the x and y directions respectively.
(A) Some of the incident wavelengths will be absent in A.
(B) Only those wavelengths will be present in B which are absent in A.
(C) B will contain some visible light.
(D) B will contain some infrared light.
Q.6 If radiation of allow wavelengths from ultraviolet to infrared is passed through hydrogen agas at room
temperature, absorption lines will be observed in the :
(A) Lyman series (B) Balmer series (C) both (A) and (B) (D) neither (A) nor (B)
Q.7 In the hydrogen atom, if the reference level of potential energy is assumed to be zero at the ground state
level. Choose the incorrect statement.
(A) The total energy of the shell increases with increase in the value of n
(B) The total energy of the shell decrease with increase in the value of n.
(C) The difference in total energy of any two shells remains the same.
(D) The total energy at the ground state becomes 13.6 eV.
Q.8 Choose the correct statement(s) for hydrogen and deuterium atoms (considering motion of nucleus)
(A) The radius of first Bohr orbit of deuterium is less than that of hydrogen
(B) The speed of electron in the first Bohr orbit of deuterium is more than that of hydrogen.
(C) The wavelength of first Balmer line of deuterium is more than that of hydrogen
(D) The angular momentum of electron in the first Bohr orbit of deuterium is more than that of hydrogen.
Q.9 Let An be the area enclosed by the nth orbit in a hydrogen atom. The graph of ln (An/A1) agains ln (n).
(A) will pass through origin
(B) will be a stright line will slope 4
(C) will be a monotonically increasing nonlinear curve
(D) will be a circle.
Q.10 A neutron collides head-on with a stationary hydrogen atom in ground state. Which of the following
statements are correct (Assume that the hydrogen atom and neutron has same mass) :
(A) If kinetic energy of the neutron is less than 20.4 eV collision must be elastic.
(B) If kinetic energy of the neutron is less than 20.4 eV collision may be inelastic.
(C) Inelastic collision may be take place only when initial kinetic energy of neutron is greater than 20.4 eV.
(D) Perfectly inelastic collision can not take place.
Q.11 When a nucleus with atomic number Z and mass number A undergoes a radioactive decay process:
(A) both Z and A will decrease, if the process is decay
(B) Z will decrease but A will not change, if the process is + decay
(C) Z will decrease but A will not change, if the process is – decay
(D) Z and A will remain unchanged, if the process is decay.
Q.12 In a Coolidge tube experiment, the minimum wavelength of the continuous X-ray spectrum is equal to
66.3 pm, then
(A) electrons accelerate through a potential difference of 12.75 kV in the Coolidge tube
(B) electrons accelerate through a potential difference of 18.75 kV in the Coolidge tube
(C) de-Broglie wavelength of the electrons reaching the anticathode is of the order of 10m.
(D) de-Broglie wavelength of the electrons reaching the anticathode is 0.01Å.
Q.13 The potential difference applied to an X-ray tube is increased. As a result, in the emitted radiation:
(A) the intensity increases (B) the minimum wave length increases
(C) the intensity decreases (D) the minimum wave length decreases
Q.14 When the atomic number A of the nucleus increases
(A) initially the neutronproton ratio is constant = 1
(B) initially neutronproton ratio increases and later decreases
(C) initially binding energy per nucleon increases and later decreases
(D) the binding energy per nucleon increases when the neutronproton ratio increases.
20
Q.15 Let mp be the mass of a proton, mn the mass of a neutron, M1 the mas of a 10 Ne nucleus and M2 the
mass of a 40
20 Ca nucleus. Then
(A) M2 = 2M1 (B) M2 > 2M1 (C) M2 < 2M1 (D) M1 < 10(mn + mp)
–1
Q.16 The decay constant of a radio active substance is 0.173 (years) . Therefore :
(A) Nearly 63% of the radioactive substance will decay in (1/0.173) year.
(B) half life of the radio active substance is (1/0.173) year.
(C) one -forth of the radioactive substance will be left after nearly 8 years.
(D) all the above statements are true.
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ANSWER KEY
Q.1 A,C Q.2 B Q.3 B Q.4 A,C,D
Q.5 A,C,D Q.6 A Q.7 B Q.8 A
Q.9 A,B Q.10 A,C Q.11 A,B,D Q.12 B
Q.13 A,D Q.14 A,C Q.15 C,D Q.16 A,C
