List of top Physics Questions

'\(x\)' joule of heat is incident on a body. Out of it, the total heat reflected and transmitted by it is '\(y\)' joule. The absorption coefficient of the body is
In an external environment of temperature (\(T\)) kelvin, a sphere at temperature (\(3T\)) kelvin has cooling rate \(R_1\). When the temperature of that sphere falls to (\(2T\)) kelvin, the cooling rate \(R_2\) of the sphere will become
Consider two rods 1 and 2 of same length. They have different specific heats \((C_1,C_2)\), thermal conductivities \((K_1,K_2)\) and area of cross-section \((A_1,A_2)\) respectively. Both the rods have temperatures \((T_1,T_2)\) at their ends. If their rate of loss of heat due to conduction is equal, then
A soap bubble of radius \(\frac{1}{\sqrt{π}}\) cm is expanded to radius \(\frac{3}{\sqrt{π}}\) cm. Surface tension of soap solution is 25 dyne/cm. The work done during expansion in erg is
The speed with which the earth would have to rotate about its axis so that a person on the equator would weigh \(\frac{3}{5}\)th as much as at present is (\(g\) = gravitational acceleration, \(R\) = equatorial radius of the earth.)
Four point masses m, 2m, 3m and 4m are kept at the corners A, B, C and D respectively of a square ABCD of side '\(b\)'. The moment of inertia of the system about an axis perpendicular to the plane of the square and passing through the point D is
A system of five solid spheres each of mass '\(m\)' and radius '\(r\)' are rotating about an axis AA' as shown in figure. Hence the moment of inertia of the system about the axis of rotation AA' is
Two balls A and B are projected at an angle of \(45^{\circ}\) and \(60^{\circ}\) respectively, so that the maximum heights reached are same for both. The ratio of initial velocity of projection of ball A to that for ball B is
\((sin30^{\circ} = cos60^{\circ} = \frac{1}{2}, sin45^{\circ} = cos45^{\circ} = \frac{1}{\sqrt{2}}, sin60^{\circ} = cos30^{\circ} = \frac{\sqrt{3}}{2})\)
Three identical spheres, each of mass 'm' kg, are kept as shown in the figure, touching each other, with their centers on a straight line. If their centers are marked as A, B, C respectively, the distance of center of mass of the system from A is
Two bodies A and B have moment of inertia \(I_A\) and \(I_B\), and angular momenta \(L_A\) and \(L_B\) respectively. Both of them have same kinetic energy of rotation. So the ratio \(L_A\) to \(L_B\) is
Mass and volume of a body are found to be \((6.00\pm 0.03)\) kg and \((2.00\pm 0.02)\) \(\text{m}^3\) respectively. Then the density of a body is
Resultant of two vectors \(\overset{⃗}{P}\) and \(\overset{⃗}{Q}\) is of magnitude A. If \(\overset{⃗}{Q}\) is reversed, then the resultant is of magnitude B. The value of \(A^2+B^2\) is
An electron makes a transition from an excited state to the ground state of a hydrogen like atom. Out of the following statements which one is correct ?
(A) K.E, P. E. and T.E. decreases
(B) K.E. increases but P. E. and T.E. decreases
(C) K.E. and T.E. decreases but P.E. increases
(D) K.E. decreases, P.E. increases but T.E. remains the same
The ratio of the density of oxygen nucleus \((_8^{16}\text{O})\) and helium nucleus \((_2^4\text{He})\) is
A photoemissive substance is illuminated with a radiation of wavelength \(λ_i\) so that it releases electrons with de-Broglie wavelength \(λ_e\). The longest wavelength of radiation that can emit photoelectron is \(λ_0\). Expression for de-Broglie wavelength is (m = mass of electron, h = Planck's constant, C = Speed of light)
Electrical conductivity of insulators is
Which of the following statement is NOT correct in the case of LED?
(A) It is a heavily doped p-n junction diode.
(B) It emits light only when it is forward biased.
(C) It emits light only when it is reverse biased.
(D) The energy of the light emitted is equal to or slightly less than the energy gap of the semiconductor used.
In which of the logic gate the following statement is true? "The output is high when either of the inputs is high but not if both inputs are high"
A ray of light passes from the vacuum into a medium of refractive index 'n'. If the angle of incidence is twice the angle of refraction, then the angle of incidence in terms of refractive index is
Three identical polaroids \(P_1\), \(P_2\) and \(P_3\) are placed one after another. The pass axis of \(P_2\) and \(P_3\) are inclined at angle of \(60^{\circ}\) and \(90^{\circ}\) with respect to axis of \(P_1\). The source has an intensity \(I_0\). The intensity of light finally coming out is
When a light of wavelength '\(λ\)' falls on the emitter of a photosensitive surface, maximum speed of emitted photoelectrons is 'V'. If the incident wavelength is changed to '\(2λ/3\)', maximum speed of emitted photoelectrons will be
In Young's double slit experiment, two slits are illuminated with a light of wavelength \(λ\). The line joining \(A_1P\) is perpendicular to \(A_1A_2\) as shown in figure. If the first minimum is detected at P, the value of slits separation 'a' will be
(D = distance between source and screen)
A convex lens having refractive index 1.6 has focal length 12 cm, when it is in air. The focal length of that lens when placed in water is (refractive index of water = 1.28)
A circular coil of radius 'r' is placed on another circular coil whose radius is 'R' and the current flowing through it is changing and their centers coincide. (\(R≫r\)). If both the coils are coplanar, then the mutual inductance between them is proportional to
An inductor of inductance \(2 μ\text{H}\) is connected in series with a resistance, a variable capacitor and an a.c. source of 10 kHz. The value of capacitance for which maximum current is drawn in to the circuit is \(\frac{1}{x} \text{F}\), where the value of x is (Take \(π^2 = 10\))