From the following, choose the element for impurity atoms with which pure silicon should be doped to make it a p-type semiconductor:

A rod of infinite length is placed along the axis of a concave mirror of focal length f.
The near end of the rod is at a distance u > f from the mirror. The length of its image is:

For what distance is ray optics a good approximation when the aperture is 3 mm wide and the wavelength is 500 nm?

A metal foil of thickness (3/4)d is introduced between two plates of a capacitor of capacitance C. The distance between the plates of the capacitor is d. The new capacitance of the capacitor will be

The frequencies of a.c. generator depends on :

In a Wheatstone Bridge, all the four arms have equal resistance r. If the resistance of the galvanometer arm is also equal to r, the equivalent resistance of the combination will be

Which of the following is not true for the image found in a plane mirror?
The image is:

A ray of light strikes a glass plate at an angle of \(60^{\circ}\). If the reflected and refracted rays are perpendicular to each other then the refractive index of glass is

Match List-I with List-II

List-I	List-II
(A) Rutherford	(I) Nuclear model of atom
(B) A.H. Becquerel	(II) Plum-Pudding Model of atom
(C) Niels Bohr	(III) Radioactivity
(D) J.J. Thomson	(IV) Hydrogen atom model

Choose the correct answer from the options given below :

Which one of the following structures is not the male sex accessory duct in human?

A proton is moving in a circular path in a magnetic field perpendicular to its plane. It possesses kinetic energy E. If the magnetic field increases to four times and the proton moves in same circular path, what will be kinetic energy?

Which of the following does not come under the category of assisted reproductive technologies?

Read the passage carefully. Attempt the questions.
In our body, cell growth and differentiation is highly controlled and regulated. In cancer cells, there is breakdown of these regulatory mechanisms. Cancerous cells just continue to divide giving rise to masses of cells called tumors. Benign tumors normally remain confined to their original location. The malignant tumors, on the other hand are a mass of proliferating cells. These cells actively divide and starve the normal cells by competing for vital nutrients. Cells sloughed from such tumors reach distant sites through blood, and wherever they get lodged in the body, they start a new tumor there. This property is called metastasis. Transformation of normal cells into cancerous cells may be induced by physical, chemical or biological agents called carcinogens.
Tobacco smoke been identified as a major cause of: