Ray Optics and Optical Instruments — Physics STD 12 Science — Question

A square coil   area is placed perpendicular to a uniform magnetic field of intensity . The magnetic flux through the coil is

(a) 10 weber

(b)  weber

(c)  weber

(d) 100 weber

In order to pass 10% of main current through a moving coil galvanometer of 99 ohm, the resistance of the required shunt is

(a) 9.9 Ω

(b) 10 Ω

(c) 11 Ω

(d) 9 Ω

A free electron is placed in the path of a plane electromagnetic wave. The electron will start moving:

A particle of charge q and mass m is moving along the x -axis with a velocity v and enters a region of electric field E and magnetic field B as shown in figure below for which figure the net force on the charge may be zero

(a)

(b)

(c)

(d)

​​​​50% of the X-rays coming from a Coolidge tube are able to pass through a 0.1mm thick aluminium foil. If the potential difference between the target and the filament is increased, the fraction of the X-rays passing through the same foil will be:

If the current in the circuit for heating the filament is increased, the cutoff wavelength:

1. Will increase.
2. Will decrease.
3. Will remain unchanged.
4. Will change.

If T is the half life of a radioactive material, then the fraction that would remain after a time   is

(a)

(b)

(c)

(d)

Two ions have equal masses but one is singly-ionised and the other is doubly-ionised. They are projected from the same place in a uniform magnetic field with the same velocity perpendicular to the field.

1. Both ions will move along circles of equal radii.
2. The circle described by the singly-ionised charge will have a radius that is. double that of the other circle.
3. The two circles do not touch each other.
4. The two circles touch each other.

Figure shows the electric lines of force emerging from a charged body. If the electric field at A and B are   and   respectively and if the displacement between A and B is r then

(a)

(b)

(c)

(d)