Nuclei — Physics STD 12 Science — Question

When hydrogen atom is in its first excited level, it’s radius is:

A spherical surface of radius of curvature R separates air (refractive index 1.0) from glass (refractive index 1.5). The centre of curvature is in the glass. A point object P placed in air is found to have a real image Q in the glass. The line PQ cuts the surface at a point O, and PO = OQ. The distance PO is equal to (a) 5 R(b) 3 R(c) 2 R(d) 1.5 R

The magnetic compass is not useful for navigation near the magnetic poles because(a) The magnetic field near the poles is zero(b) The magnetic field near the poles is almost vertical(c) At low temperature, the compass needle looses its magnetic properties(d) Neither of the above

A conductor with a positive charge (a) Is always at +ve  potential(b) Is always at zero potential(c) Is always at negative potential(d) May be at +ve, zero or -ve potential

Electroscope is used:

Two cells of emf’s approximately 5V and 10V are to be accurately compared using a potentiometer of length 400cm.

A element used for radioactive carbon dating for more than 5600 years is(a) C - 14 (b) U - 234(c) U - 238(d) Po - 94

A metal sheet is placed in front of a strong magnetic pole. A force needed to:

The light reflected by a plane mirror may form a real image(a) If the rays incident on the mirror are diverging(b) If the rays incident on the mirror are converging(c) If the object is placed very close to the mirror (d) Under no circumstances