List of top Physics Questions asked in BITSAT

After two hours, one-sixteenth of the starting amount of a certain radioactive isotope remained undecayed. The half life of the isotope is

Two plano-concave lenses $(1$ and $2)$ of glass of refractive index $1.5$ have radii of curvature $25 \,cm$ and $20 \,cm$. They are placed in contact with their curved surface towards each other and the space between them is filled with liquid of refractive index $4/3$. Then the combination is

A sonometer wire resonates with a given tuning fork forming standing waves with five antinodes between the two bridges when a mass of $9 \,kg$ is suspended from the wire. When this mass is replaced by a mass $M$, the wire resonates with the same tuning fork forming three antinodes for the same positions of the bridges. The value of $M$

A capillary tube of radius $R$ is immersed in water and water rises in it to a height $H$. Mass of water in the capillary tube is $M$. If the radius of the tube is doubled, mass of water that will rise in the capillary tube will now be :

A mercury drop of radius $1 \,cm$ is sprayed into $10^{6}$ drops of equal size. The energy expended in joule is (surface tension of mercury is $460 \times 10^{-3}\,N / m$ ):

When a metal surface is illuminated by light of wavelengths $400\, nm$ and $250\,nm$, the maximum velocities of the photoelectrons ejected are $V$ and $2 V$ respectively. The work function of the metal is

On a hypotenuse of a right prism $\left(30^{\circ}-60^{\circ}-90^{\circ}\right)$ of refractive index $1.50$, a drop of liquid is placed as shown in figure. Light is allowed to fall normally on the short face of the prism. In order that the ray of light may get totally reflected, the maximum value of refractive index is :

Steel wire of length ' $L$ ' at $40^{\circ} C$ is suspended from the ceiling and then a mass ' $m$ ' is hung from its free end. The wire is cooled down from $40^{\circ} C$, to $30^{\circ} C$ to regain its original length '$L$'. The coefficient of linear thermal expansion of the steel is $10^{-5} /{ }^{\circ} C$, Young's modulus of steel is $10^{11} \,N / m ^{2}$ and radius of the wire is $1 \,mm$. Assume that $L \gg$ diameter of the wire. Then the value of ' $m$ ' in $kg$ in nearly.

Two concentric conducting thin spherical shells $A$ and $B$ having radii $r _{ A }$ and $r _{ B }\left( r _{ B }> r _{ A }\right)$ are charged to $Q _{ A }$ and $- Q _{ B }\left(\left| Q _{ B }\right|>\left| Q _{ A }\right|\right)$. The electrical field along a line passing through the centre is

Two very long, straight, parallel wires carry steady currents $ I$ and $-I$ respectively. The distance between the wires is $d$. At a certain instant of time, a point charge $q$ is at a point equidistant from the two wires, in the plane of the wires. Its instantaneous velocity $v$ perpendicular to this plane. The magnitude of the force due to the magnetic field acting on the charge at this instant is

Specific conductance of o.1 \,M \,HA is $3 \cdot 75 \times 10^{-4} \,ohm ^{-1} \, cm ^{-1}$. Find the dissociation constant $K _{ a }$ of $HA$, if $\lambda_{\infty}( HA )=250 \, ohm ^{-1} \, cm ^{2} \,mol ^{-1}:$

In the formula $X=3 Y Z^{2}, X$ and $Z$ have dimensions of capacitance and magnetic induction respectively. The dimensions of $Y$ in $MKSA$ system are :

When ${ }^{92} U _{235}$ undergoes fission $0.1 \%$ of its original mass is changed into energy. How much energy is released if $1 \,kg$ of ${ }^{92} U _{235}$ undergoes fission

A frictionless wire $A B$ is fixed on a sphere of radius $R$. A very small spherical ball slips on this wire. The time taken by this ball to slip from $A$ to $B$ is

For the angle of minimum deviation of a prism to be equal to its refracting angle, the prism must be made of a material whose refractive index :

Find the number of photon emitted per second by a $25$ watt source of monochromatic light of wavelength $ 6600\, ??. What is the photoelectric current assuming $3\%$ efficiency for photoelectric effect ?

Two identical charged spheres suspended from a common point by two massless strings of lengths $l$, are initially at a distance $d(d < < l)$ apart because of their mutual repulsion. The charges begin to leak from both the spheres at a constant rate. As a result, the spheres approach each other with a velocity $v$. Then $v$ varies as a function of the distance $x$ between the spheres, as:

A source of sound $S$ emitting waves of frequency $100\, Hz$ and an observor $O$ are located at some distance from each other. The source is moving with a speed of $19.4\, m s^{-1}$ at an angle of $60^{\circ}$ with the source observer line as shown in the figure. The observor is at rest. The apparent frequency observed by the observer is (velocity of sound in air $330\, ms ^{-1}$ )

A capillary tube of radius $r$ is immersed vertically in a liquid such that liquid rises in it to height $h$ (less than the length of the tube). Mass of liquid in the capillary tube is $m$. If radius of the capillary tube is increased by $50 \%$, then mass of liquid that will rise in the tube, is

A string of length $\ell$ is fixed at both ends. It is vibrating in its $3^{rd}$ overtone with maximum amplitude '$a$'. The amplitude at a distance $\ell /3$ from one end is.

A ray of light of intensity $I$ is incident on a parallel glass slab at point $A$ as shown in diagram. It undergoes partial reflection and refraction. At each reflection, $25 \%$ of incident energy is reflected. The rays $A B$ and $A^{\prime} B^{\prime}$ undergo interference. The ratio of $I_{\max }$ and $I_{\min }$ is :

A deuteron of kinetic energy $50 \,keV$ is describing a circular orbit of radius $0.5$ metre in a plane perpendicular to the magnetic field $B$. The kinetic energy of the proton that describes a circular orbit of radius $0.5$ metre in the same plane with the same $B$ is