The magnetic field at the point of intersection of diagonals of a square wire loop of side L carrying a current I is
Four charges equal to -Q are placed at the four corners of a square and a charge q is at its centre. If the system is in equilibrium, the value of q is
A radioactive nucleus of mass number A, initially at rest, emits an α-particle with a speed v. The recoil speed of the daughter nucleus will be
In the nuclear reaction , the X will be
D.
In the reaction, we have to conserve the mass number and the atomic number. Thus,we have
So, 14 + a = 14 + 1
Hence a = 1 and 7 + b = 6 + 1
Hence b = 0.
So, we have
In Young's double slit experiment the two slits are d distance apart. Interference pattern is observed on a screen at a distance D from the slits. A dark fringe is observed on the screen directly opposite to one of the slits. The wavelength of light is
Two thin lenses of focal lengths 20 cm and 25 cm are placed in contact. The effective power of the combination is
9 D
2 D
3 D
7 D
A convex lens of focal length 30 cm produces 5 times magnified real image of an object. What is the object distance?
36 cm
25 cm
30 cm
150 cm
If the focal length of the eye-piece of a telescope is doubled, its magnifying power (m) will be
2 m
3 m
4 m
A plano-concave lens is made of glass of refractive index 1.5 and the radius of curvature of its curved face is 100 cm. What is the power of the lens ?
+ 0.5 D
− 0.5 D
− 2 D
+ 2 D