CSIR-JRF/NET Physics
Atomic, Molecular physics and more.... Test 24
Answer all questions Time
20 min
Max
20 marks
1.
The law of Malus in polarisation is ---
a)
I=I0Cos2θ* (b) ) I=I0Cosθ
(c) )
I=I0Cos2(90-θ) (d) ) I=I0Cos(90-θ)
2. Which of
the following decay is possible?
(a)π+ → μ-
+ νμ (b) π - → π+
+e- + e+
(c) π0
→ e- + p (d) n → p+
e- + νe(bar)*
3. A radioactive nucleus A has a mean life of 10s.
The nucleus decays into its daughter B. The mean life of B is 10 years.
Starting with 1022 nuclei of A at t=0, the rate of decay of B at t=1
year is most nearly----
(a)1022/y (b) 1021/y* (c) 1020/y (d) 1019/y
Hint: dN/dt=λN=N/τ; dN/dt=1022
/10
= 1021per yea;
4. The
most reasonable approximation for the for the ratio of the density of nuclear
matter to the density of water is---
(a)1 (b) 1000 (c)106 (d)
1014*
5. The
mean KE of electrons in metals many times the thermal energy kT. Which of the
following can be best be used to explain this fact?
(a)
The uncertainly relation (b) Pauli’s exclusion principle*
(c)
degeneracy of the energy levels (d)
The born approximation
6. The
natural line width of an atomic transition with mean life time of 5ns is nearly
(a) 4.1x10-15eV (b)
1.2x10-11eV (c) 1.3x10-7eV* (d)
1.2x10-21eV
Hint:
ΔE. Δt ≥ħ
7. In
nuclear instrumentation which is heaviest and slow moving particles------
(a) beta particles (b) gamma rays (c) alpha particles* (d) neutrons
8. Bragg
reflection from BCC structure are extinguished if the Miller indices (hkl) are
such that
(a)
h+k=even (b) h+k+l= odd* (c)
h+k+l=even (d)
h+k +odd
9. The temperature
transducer which can be used for detecting heat rays is---
(a)
Radiometer (b)
Thermometer
(c) Thermopile* (d)
Pyromteter
10. The
resistance of a photosensitive cell
(a) Increase with increase in light intensity (b) Remains constant with increase in
light
(c))
Decrease with increase in intensity of
light in a linear manner* (d) Decrease
with increase in intensity of light in an exponential manner
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