A parallel beam of monochromatic unpolarised light is incidenton a transparent dielectric plate of refractive index \(\frac{1}{\sqrt{3}}\). The reflected beam is completely polarised. Then the angle of incidence is

30º
60º
45º
75º

Solution

When angle of incidence i is equal to angle of polarisation i.e, then reflected light is completely plane-polarised whose vibration is perpendicular to plane of incidence

A ball is thrown vertically upward with a velocity ‘u’ from the balloon descending with velocity v.The ball will pass by the balloon after time

\(\frac{u-v}{2g}\)
\(\frac{u-v}{2g}\)
\(\frac{u-v}{2g}\)
\(\frac{u-v}{2g}\)

Solution

Angular width (B) of central maxima of a diffraction pattern of a single slit does not depend upon

distance between slit and source
wavelength of the light used
width of slit
frequency of light used

Solution

Fig. shows a disc rolling on a horizontal plane with linear velocity v. Its linear velocity is v and angular velocity is ω.Which of the following gives the velocity of the particle P on the rim of the disc

v (1 + cos θ)
v (1 - cos θ)
v (1 + sin θ)
v (1 - sin θ)

Solution

Velocity of P = (NP)ω = (NM + MP)ω

= r(r + sin θ)ω = v(1 + sinθ)

An electron is

hadron
baryon
a nucleon
a lepton.

Solution

An electron is a lepton.

When red glass is heated in dark room, it will seem

green
purple
black
yellow

Solution

When a red glass is heated to a high temperature it will glow with green light.

An electric dipole is placed along the x-axis at the origin O.A point P is at a distance of 20 cm from this origin such that OP makes an angle π/3 with the x-axis. If the electric field at P makes an angle q with the x-axis, the value of θ would be

^π⁄₃
\(\frac{\pi }{3}+tan^{-1}\left ( \frac{\sqrt{3}}{2} \right )\)
^2π⁄₃
\(tan^{-1}\left ( \frac{\sqrt{3}}{2} \right )\)

Solution

A body of mass 5kg falls from a height of 20 metres on the ground and it rebounds to a height of 0.2 m. If the loss in potential energy is used up by the body,then what will be the temperature rise?(specific heat of material = 0.09 cal gm^-1ºC^-1)

0ºC
4ºC
8ºC
None of these

Solution

Outside a nucleus

neutron is stable
proton and neutron both are stable
neutron is unstable
neither neutron nor proton is stable

Solution

Out side the nucleus, neutron is unstable (life ≈ 932s).

The relation between time t and distance x is t = αx²x + βx where α and β are constants. The retardation is

2αv³
2βv³
2αβv³
2β²v³

Solution

Two resistances R₁ and R₂ are made of different materials.The temperature coefficient of the material of R₁ is α and that of material of R₂ is– β. The resistance of the series combination of R₁ and R₂ will not change with temperature if ^R₁⁄_R₂ equal to

^α⁄_β
\(\frac{\alpha +\beta }{\alpha -\beta }\)
\(\frac{\alpha^{2} +\beta^{2} }{2 \alpha \beta }\)
^β⁄_α

Solution

A Carnot’s engine works as a refrigerator between 250 K and 300 K. If it receives 750 calories of heat from the reservoir at the lower temperature, the amount of heat rejected at the higher temperature is

900 calories
625 calories
750 calories
1000 calories

Solution

\(\frac{750}{W}=\frac{250}{300-250}\)

Heat rejected = 750 + 150 = 900 cal.

The Fraunhoffer ‘diffraction’ pattern of a single slit is formed in the focal plane of a lens of focal length 1 m. The width of slit is 0.3 mm. If third minimum is formed at a distance of 5mm from central maximum, then wavelength of light will be

5000 Å
2500 Å
7500 Å
8500 Å

Solution

Direction: Each question contains STATEMENT-1 and STATEMENT-2. Choose the correct answer(ONLY ONE option is correct ) from the following-

Statement 1: Two convex lenses joined together can not produce an achromatic combination.

Statement 2: The condition for achromatism is \(\frac{\omega _{1}}{f_{1}}+\frac{\omega _{2}}{f_{2}}=0\) where symbols have their usual meaning.

(a)Statement -1 is false, Statement-2 is true
(b)Statement -1 is true, Statement-2 is true; Statement -2 is a correct explanation for Statement-1
(c)Statement -1 is true, Statement-2 is true; Statement-2 is not a correct explanation for Statement-1
(d)Statement -1 is true, Statement-2 is false

The oscillating electric and magnetic vectors of an electromagnetic wave are oriented along

the same direction but differ in phase by 90°
the same direction and are in phase
mutually perpendicular directions and are in phase
mutually perpendicular directions and differ in phase by 90°

Solution

\(\overrightarrow{E}\) and \(\overrightarrow{B}\) are mutually perpendicular to each other and are in phase i.e., they become a zero and minimum at the same place and at the same time.

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