Semiconductor Electronic: Material, Devices And Simple Circuits — Physics STD 12 Science — Question

The line of force in a magnetic field represents the direction at each point that a magnetic needle placed at the point takes up. Do they also represent the direction of the force on a moving charge at each point?

The photoelectric threshold wavelength of a certain metal is 3000Å. If the radiation of 2000Å is incident on the metal

(a) Electrons will be emitted	(b) Positrons will be emitted
(c) Protons will be emitted	(d) Electrons will not be emitted

Comment on the statement given below:
In self-inductionWhen the current in a coil is increasing, induced emf opposes it
When the current in a coil is decreasing, induced emf supports it

A Young's double slit experiment uses a monochromatic source. The shape of the interference fringes formed on a screen is

(a) Straight line

(b) Parabola

(c) Hyperbola

(d) Circle

By keeping a conductor in an external electric field and from the result obtained by electrostatics, which of the following options is wrong?

Which of the following spectral series in hydrogen atom give spectral line of 4860 Å

(a) Lyman

(b) Balmer

(c) Paschen

(d) Brackett

SI unit of the magnetic field is _________.

A thin convex lens of refractive index 1.5 has a focal length of 15 cm in air. When the lens is placed in liquid of refractive index 4/3 , its focal length will be

(a) 15 cm

(b) 10 cm

(c) 30 cm

(d) 60 cm

Which of the following could not produce a virtual image

(a) Plane mirror

(b) Convex mirror

(c) Concave mirror

(d) All the above can produce a virtual image

A wire of resistance R is divided in 10 equal parts. These parts are connected in parallel, the equivalent resistance of such connection will be

(a) 0.01 R

(b) 0.1 R

(c) 10 R

(d) 100 R