Physics Test

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Physics Test - 22

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Question 1
1 / -0

A beam of light AO is incident on a glass slab $(μ = 1.54)$ in a direction as shown in figure. The reflected ray OB is passed through a Nicol prism. On viewing through a Nicole prism, we find on rotating the prism that: [tan 57^o= 1.54]

A
The intensity is reduced down to zero and remains zero

B
The intensity reduces down some what and rises again

C
There is no change in intensity

D
The intensity gradually reduces to zero and then again increases

Solution

Polarizing angle, θ, is tanθ = μ ⇒ θ = 57^∘

n the arrangement shown, the unpolarised light is incident at polarizing angle of 90^∘ − 33^∘ = 57^∘

The reflected light is thus plane polarized light and is passed through Nicol prism (a polarizer or analyser), the intensity gradually reduces to zero and finally increases.
Question 2
1 / -0

Distance in free space at which intensity of 5 eV neutron beam reduces to half will be nearly : (Take half life of neutron = 12.8 min)

A
6000 km

B
12000 km

C
18000 km

D
24000 km

Solution
Question 3
1 / -0

Current I is flowing in an equilateral triangular loop of side length L as shown in figure. The magnetic field produced at the centroid of the loop is

A
$\frac{3 \sqrt{3} μ_{0} I}{2 π L}$

B
$\frac{9 μ_{0} I}{2 π L}$

C
$\frac{μ_{0} I}{3 \sqrt{3} π L}$

D
$\frac{\sqrt{3} μ_{0} I}{2 π L}$

Solution
Question 4
1 / -0

The reading of ideal ammeter in the circuit is

A
$1 A$

B
$2 A$

C
$3 A$

D
$5 A$

Solution

Since ideal ammeter has zero resistor hence the current will flow through ammeter and not through the
Question 5
1 / -0

A body of mass 25 kg is at rest on a horizontal surface. Minimum horizontal force required to just start motion is 73.5 N and a force of 49 N is needed to keep the body moving with a constant velocity. What is the coefficient of static friction?

A
0.2

B
0.3

C
0.4

D
0.5

Solution

m = 25 kg
Coefficient of static friction
$= μ_{s} = \frac{Limiting friction}{m g} = \frac{73.5/(}{25 \times 9.8)} = 0.3$
Question 6
1 / -0

The age of the wood if only $\frac{1}{16}$part of original$\mathrm{C}^{14}$is present in its piece is ($T_{1 / 2}$of $\mathrm{C}^{14}$is 5580 years)

A
5580 years

B
11160 years

C
22320 years

D
16740 years

Solution

Fraction of atoms left after $n$ half-lives, $\frac{N}{N_{0}}=\left(\frac{1}{2}\right)^{n}$
$\frac{1}{16}=\frac{1}{2^{4}}$
$\Rightarrow n=4$
$\therefore$ age $=4 \times 5580$ years
$=22320$ years
Question 7
1 / -0

Two particles of masses $m_{1}$ and $m_{2}$ have equal kinetic energies. The ratio of their momenta is

A
$m_{1} : m_{2}$

B
$m_{2} : m_{1}$

C
${\sqrt{m_{1}}}_{} : {\sqrt{m_{2}}}_{}$

D
$m_{1}^{2} : m_{2}^{2}$

Solution

$\frac{p_{1}^{2}}{2 m_{1}}=\frac{p_{2}^{2}}{2 m_{2}}$
$p_{1}, p_{2}$ are momenta; $m_{1}$ and $m_{2}$ are masses of two particles respectively.
$\frac{p_{1}}{p_{2}}=\sqrt{\frac{m_{1}}{m_{2}}}$
Question 8
1 / -0

A voltage of peak value $283 \mathrm{V}$ and varying frequency is applied to a series LCR combination in which $\mathrm{R}=3 \Omega, L=25 \mathrm{mH}$ and $\mathrm{C}=400 \mu \mathrm{F}$. The frequency $f$ (in $\mathrm{Hz}$ )of the source at which maximum power is dissipated in the above, is

A
48.4

B
52.7

C
47.4

D
50.3

Solution
Question 9
1 / -0

A wave has velocity $u$ in medium $P$ and velocity $2 u$ in medium $Q$. If the wave is refracted from medium $P$ to medium $Q$ at an angle of incidence $b$ then the angle of refraction will be

A
a

B
d

C
c

D
b

Solution