Nucleus — Physics STD 12 Science — Question

Diffraction of light can be explained by the following:

A beam of monochromatic blue light of wavelength 4200Å in air travels in water (μ = 4/3). Its wavelength in water will be

(a) 2800 Å

(b) 5600 Å

(c) 3150 Å

(d) 4000 Å

Magnetic lines of force can pass through:

A magnet is suspended in such a way that it oscillates in the horizontal plane. It makes 20 oscillations per minute at a place where dip angle is 30^o and 15 oscillations per minute at a place where dip angle is 60^o. The ratio of total earth's magnetic field at the two places is

(a) 3

(b) 16 : 9

(c) 4 : 9

(d) 2

Which of the following statement is incorrect

(a) Both ac and dc dynamo have a field magnet

(b) Both ac and dc dynamo have an armature

(c) Both ac and dc dynamo convert mechanical energy into electrical energy

(d) Both ac and dc dynamo have slip rings

Photo cell is  a device to

(a) Store photons

(b) Measure light intensity

(c) Convert photon energy into mechanical energy

(d) Store electrical energy for replacing storage batteries

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:

A bar magnet is released from rest along the axis of a very long, vertical copper tube. After some time the magnet:

1. Will stop in the tube.
2. Will move with almost content speed.
3. Will move with an acceleration g.
4. Will oscillate.

According to Bohr's theory the radius of electron in an orbit described by principal quantum number n and atomic number Z is proportional to

(a)

(b)

(c)

(d)