Wave Optics — Physics STD 12 Science — Question

Which of the following statements given below is not true in the context of magnetic lines of force?

Radius of central zone of circular zone plate is 2.3 mm. Wavelength of incident light is 5893.  Source is at a distance of 6m  Then the distance of first image will be

(a) 9 m

(b) 12 m

(c) 24 m

(d) 36 m

An ionised H-molecule consists of an electron and two protons. The protons are separated by a small distance of the order of angstrom. In the ground state:

If the field lines in a magnetic field are parallel and equidistant, the magnetic field is __________ .

Two electric bulbs whose resistances are in the ratio of 1 : 2 are connected in parallel to a constant voltage source. The powers dissipated in them have the ratio

(a) 1 : 2

(b) 1 : 1

(c) 2 : 1

(d) 1 : 4

A convex lens of focal length 0.5 m and concave lens of focal length 1 m are combined. The power of the resulting lens will be

(a) 1 D

(b) – 1 D

(c) 0.5 D

(d)  – 0.5 D

If a magnet is hanged with its magnetic axis then it stops in

(a) Magnetic meridian	(b) Geometric meridian
(c) Angle of dip	(d) None of these

When subjected to a transverse electric field, cathode rays move

(a) Down the potential gradient	(b) Up the potential gradient
(c) Along a hyperbolic path	(d) Along a circular path

Due to the flow of current in a circular loop of radius R, the magnetic induction produced at the centre of the loop is B. The magnetic moment of the loop is (

(a)

(b)

(c)

(d)