The image formed by an objective of a compound microscope is
An astronomical telescope has a large aperture to
Which of the following is used in optical fibres?
Wavelength of light used in an optical instrument are 
= 4000 Å and 
= 5000 Å, then ratio of their respective resolving powers (corresponding to and ) is
If two mirrors are kept at 60° to each other, then the number of images formed by them is
Which of the following is used in optical fibers?
In total internal reflection when the angle of incidence is equal to the critical angle for the pair of media in contact, what will be angle of refraction?
Two similar thin equi-convex lenses, of focal length f each, are kept coaxially in contact with each other such that the focal length of the combination is F1. When the space between the two lenses is filled with glycerin (which has the same refractive index (μ = 1.5) as that of glass) then the equivalent focal length is F2.TheratioF1 :F2 willbe:
Ranker question 2. If we live in a three dimensional world (x-y-z) , why is r squared and not cubed?
Which of the following nuclear reactions will generate an isotope?
A radioactive element gets spilled over the floor of a room. Its halflife period is 30 days. If the initial velocity is ten times the permissible value, after how many days will it be safe to enter the room?
In the transformation of 
, if one emission is an alpha particle, what should be the other emission(s)?
A photon of hard gamma radiation knocks a proton out of 
nucleus to form
Hydrogen bomb is based on the principle of
The halflife of a radioisotope is four hours. If the initial mass of the isotope was 200 g, the mass remaining after 24 hours undecayed is
The half life of a radioactive isotope is three hours. If the initial mass of the iosotope were 256 g, the mass of it remaining undecayed after 18 hours would be
The radionucleide 
undergoes two successive 
followed by one 
. The atomic number and the mass number respectively of the resulting radionucleide are
(beta) particle is emitted in radioactivity by
If half life of a substance is 5 yrs, then the total amount of substance left after 15 years, when initial amount is 64 grams is
In an AC generator, a coil with N turns, all of the same area A and total resistance R, rotates with frequency w in a magnetic field B. What will be the maximum value of emf generated in the coil?
In a series resonant LCR circuit, the voltage across R is 100 volts and R = 
with C = 
The resonant frequency 
is 200 rad/s. At resonance the voltage across L is
The phase difference between the alternating current and emf is 
Which of the following cannot be the constituent of the circuit?
A circuit has a resistance of 12 ohm and an impedance of 15 ohm. What will be the power factor of the circuit?
The self inductance of the motor of an electric fan is 10 H. In order to impart maximum power at 50 Hz, it should be connected to a capacitance of
One conducting U tube can slide inside another as shown in figure, maintaining electrical contacts between the tubes. The magnetic field B is perpendicular to the plane of the figure. If each tube moves towards the other at a constant speed v, then the emf induced in the circuit in terms of B, l and v where l is the width of each tube, will be
A metal conductor of length 1 m rotates vertically about one of its ends at angular velocity 5 radian per second. If the horizontal component of earth’s magnetic field is 0.2 × 10-4 T, then the e.m.f. developed between the two ends of the conductor
In a LCR circuit capacitance is changed from C to 2C. For the resonant frequency to remain unchanged, the inductance should be changed from L to
In a uniform magnetic field of induction B a wire in the form of a semicircle of radius r rotates about the diameter of the circle with angular frequency 
. The axis of rotation is perpendicular to the field. If the total resistance of the circuit is R the mean power generated per period of rotation is
A coil having n turns and resistance R 
is connected with a galvanometer of resistance 4R . This combination is moved in time t seconds from a magnetic field W1 weber to W2 weber. The induced current in the circuit is
Alternating current cannot be measured by D.C. ammeter because
In an LCR series a.c. circuit, the voltage across each of the components, L, C and R is 50 V. What will be the voltage across the LC combination?
The core of any transformer is laminated so as to
In an oscillating LC circuit the maximum charge on the capacitor is Q. The charge on the capacitor when the energy is stored equally between the electric and magnetic field is
When the current changes from +2 A to –2 A in 0.05 second, an e.m.f. of 8 V is induced in a coil. What is the coefficient of selfinduction of the coil?
Two coils are placed close to each other. The mutual inductance of the pair of coils depends upon
elative permittivity and permeability of a material are 
and 
, respectively. Which of the following values of these quantities are allowed for a diamagnetic mateiral?
Needles N1, N2 and N3 are made of a ferromagnetic, a paramagnetic and a diamagnetic substance respectively. A magnet when brought close to them will
A magnetic needle is kept in a nonuniform magnetic field. It experiences
The materials suitable for making electromagnets should have
The length of a magnet is large compared to its width and breadth. The time period of its oscillation in a vibration magnetometer is 2 s. The magnet is cut along its length into three equal parts and three parts are then placed on each other with their like poles together. What will be the time period of this combination?
There are several types of enzyme catalysed reactions. In
one type of enzyme catalysed reaction, in addition to the
catalytic site to which the substrate (X) binds, the enzyme
also has a site to which some other substance (Y) can bind.
When Y binds to such an enzyme, the enzyme can still bind
to the substrate but cannot convert it to the product. Which
of the following will occur in such a case?
In an experiment, E. coli cells growing at 37°C were shifted to 20°C and grown for a few generations. Which of the
following changes in the membrane would help the E. coli cells adapt to the new environment?
A cladogram that classifies five species (M, N, O, P and Q) is shown below.Which of the six dots in the cladogram corresponds to the most recent common ancestor of N and P?
During the growth of marine fish, initially, yolk sac and skin are the principal sites where transport protein ‘x’ is located. Later, skin and gills become principal sites and finally ‘x’ becomes localised to gills. The protein ‘x’ is
A horizontal overhead powerline is at a height of 4 m from the ground and carries a current of 100 A from east to west. The magnetic field directly below it on the ground is
Two identical conducting wires AOB and COD are placed at right angles to each other. The wire AOB carries an electric current I1 and COD carries a current I2. The magnetic field on a point lying at a distance d from O, in a direction perpendicular to the plane of the wires AOB and COD, will be given by
A charged particle moves through a magnetic field perpendicular to its direction. Then
A charged particle with charge q enters a region of constant, uniform and mutually orthogonal fields 
and 
with a velocity 
perpendicular to both and , and comes out without any change in magnitude or direction of . Then
A current I flows along the length of an infinitely long, straight, thin walled pipe. Then
What is the inductance between A and D?
