Model Paper 1 — Physics STD 12 Science — Question

The direction of ray of light incident on a concave mirror is shown by PQ while directions in which the ray would travel after reflection is shown by four rays marked 1, 2, 3 and 4 (Fig). Which of the four rays correctly shows the direction of reflected ray?

When the accelerating voltage applied on the electrons increased beyond a critical value

(a) Only the intensity of the various wavelengths is increased

(b) Only the wavelength of characteristic relation is affected

(c) The spectrum of white radiation is unaffected

(d) The intensities of characteristic lines relative to the white spectrum are increased but there is no change in their wavelength

Consider the two following statements A and B and identify the correct choice given in the answers;

(A) In photovlotaic cells the photoelectric current produced is not proportional to the, intensity of incident light.

(B) In gas filled photoemissive cells, the velocity of photoelectrons depends on the wavelength of the incident radiation.

(a) Both A and B are true	(b) Both A and B are false
(c) A is true but B is false	(d) A is false B is true

In  nucleus, there are

(a) 138 protons and 88 neutrons	(b) 138 neutrons and 88 protons
(c) 226 protons and 88 electrons	(d) 226 neutrons and 138 electrons

Among the following properties describing diamagnetism identify  the property that is wrongly stated

(a) Diamagnetic material do not have permanent magnetic moment

(b) Diamagnetism is explained in terms of electromagnetic induction

(c) Diamagnetic materials have a small positive susceptibility

(d) The magnetic moment of individual electrons neutralize each other

Which of the following statement is true about magnetic moments of atoms of different elements

(a) All have a magnetic moment

(b) None has a magnetic moment

(c) All acquire a magnetic moment under external magnetic field and in same direction as the field

(d) None of the above statements are accurate

The minimum wavelength of X-ray emitted by X-rays tube is 0.4125 Å. The accelerating voltage is

(a) 30 kV

(b) 50 kV

(c) 80 kV

(d) 60 kV

The potential at a point due to an electric dipole will be maximum and minimum when  the angles between the axis of the dipole and the line joining the point to the dipole are respectively

(a) 90° and 180 °

(b) 0°  and 90°

(c) 90 ° and 0°

(d) 0° and 180°

A nuclear reaction given by   represents

(a) g-decay

(b) Fusion

(c) Fission

(d) b-decay

A tuning fork of frequency 480Hz is used to vibrate a sonometer wire having natural frequency 240Hz. The wire will vibrate with a frequency of:

1. 240Hz
2. 480Hz
3. 720Hz
4. Will not vibrate.