Electric Charges and Fields — Physics STD 12 Science — Question

If the energy of a photon corresponding to a wavelength of 6000 Å is 3.32 , the photon energy for a wavelength of 4000 Å will be

(a) 1.4 eV

(b) 4.9 eV

(c) 3.1 eV

(d) 1.6 eV

Which is not true with respect to the cathode rays

(a) A stream of electrons	(b) Charged particles
(c) Move with speed same as that of light	(d) Can be deflected by magnetic fields

When a comb rubbed with dry hair attracts pieces of paper. This is because the.

Total internal reflection can take place only if:

1. Light goes from optically rarer medium (smaller refractive index) to optically denser medium.
2. Light goes from optically denser medium to rarer medium.
3. The refractive indices of the two media are close to each other.
4. The refractive indices of the two media are widely different.

Light of wavelength 4000 Å falls on a photosensitive metal and a negative 2V potential stops the emitted electrons. The work function of the material (in eV) is approximately (h = 6.6

(a) 1.1

(b) 2.0

(c) 2.2

(d) 3.1

An electric wire is connected across a cell of e.m.f. E. The current  I is measured by an ammeter of resistance R. According to ohm's law

(a)

(b) E = IR

(c) E = R/I

(d) E = I/R

Consider a magnetic dipole kept in the north to south direction. Let P₁, P₂, Q₁, Q₂ be four points at the same distance from the dipole towards north, south, east and west of the dipole respectively. The directions of the magnetic field due to the dipole are the same at:

1. P₁ and P₂
2. Q₁ and Q₂
3. P₁ and Q₁
4. P₂ and Q₂

To minimise the power loss in the transmission cables connecting the power stations to homes and factories, the transmission cables carry current:

The radii of two metallic spheres P and Q  are  and  respectively. They are given the same charge. If  . then on connecting them with a thin wire, the charge will flow

(a) From P to Q

(b) From Q to P

(c) Neither the charge will flow from  P to Q nor from Q to P

(d) The information is incomplete