Atoms — Physics STD 12 Science — Question

When semiconductor is doped half with trivalent and half with pentavalent impurities, junction formed is known as:

A convex lens is used to form real image of an object on a screen. It is observed that even when the positions of the object and that screen are fixed there are two positions of the lens to form real images.  If the heights of the images are 4 cm and 9 cm respectively, the height of the object is

(a) 2.25 cm

(b) 6.00 cm

(c) 6.50 cm

(d) 36.00 cm

Let nh and ne be the number of holes and conduction electrons in an extrinsic semiconductor:

A capacitor is charged by using a battery which is then disconnected. A dielectric slab is introduced between the plates which results in:

Fundamental gates are :

The equation E = pc is valid:

Which of the following form(s) a virtual and erect image for all positions of the object

(a) Convex lens

(b) Concave lens

(c) Convex mirror

(d) b, c

Time taken by the sunlight to pass through a window of thickness 4 mm whose refractive index is 1.5 is

(a) 2  sec

(b) 2 sec

(c) 2  sec

(d) 2   sec

The energy of a photon of characteristic X-rays from  a Coolidge tube comes from

(a) The kinetic energy of the striking electron

(b) The kinetic energy of the free electrons of the target

(c) The kinetic energy of the ions of the target

(d) An electronic transition of the target atom

The electromagnetic wave of highest frequency is :