Which of the followings should be doped with pure silicon to get an n-type and p-type semiconductors respectively?

A resistor develops 800 J of thermal energy in 20 s on applying a potential difference of 20 V. Its resistance is

In the electromagnetic spectrum, the visible spectrum lies between :

Figure shows a rectangular conductor PQRS in which the conductor PQ is free to move. The conductor PQ is moved towards the left with a constant velocity V as shown in the figure. Assume that there is no loss of energy due to friction. What will be the magnetic flux linked with the loop PQRS and the motional emf?

A current of 2 A flows through a plane circular coil of radius 3 cm and having 50 turns. The coil has been placed in a uniform magnetic field of 0.6 T. The minimum potential energy of the coil will be

The wavelength of light from the spectral emission line of sodium is 662 nm.
The kinetic energy at which an electron would have the same de-Broglie wavelength would be:
(Given: \( h = 6.62 \times 10^{-34} \text{ J s}, m_e = 9 \times 10^{-31} \text{ kg} \))

In a concave mirror, an object is placed at a distance \( x \) from the focus and the image is formed at a distance \( y \) from the focus. What is the focal length of the mirror?

A wire of resistance \( 18 \, \Omega \) is bent in the form of an equilateral triangle. The effective resistance between any two corners of the triangle is :

Read the following paragraph and answer the given questions.
RNAi takes place in all eukaryotic organisms as a method of cellular defense. The source of this complementary RNA could be from an infection by viruses having RNA genomes or mobile genetic elements (transposons) that replicate via an RNA intermediate. Insulin from an animal source, though caused some patients to develop allergy or other types of reactions to the foreign protein. Insulin consists of two short polypeptide chains: chain A and chain B, that are linked together by disulphide bridges. Transgenic mice are being developed for use in testing the safety of vaccines before they are used on humans. Transgenic mice are being used to test the safety of the polio vaccine. If successful and found to be reliable, they could replace the use of monkeys to test the safety of batches of the vaccine. Specific Bt toxin genes were isolated from Bacillusthuringiensis} and incorporated into the several crop plants such as cotton. The choice of genes depends upon the crop and the targeted pest, as most Bt toxins are insect-group specific. The toxin is coded by a gene cryIAc named cry. There are a number of them, for example, the proteins encoded by the genes cryIAc and cryIIAb control the cotton bollworms, that of cryIAb controls corn borer.

The transgenic mice are being used to test the safety of which vaccine?

Identify the correct pKa value order:
A. Phenol
B. 4-Methylphenol (p-Cresol)
C. Benzoic acid
D. 4-Methylbenzoic acid
E. 4-Nitrobenzoic acid
Choose the correct answer from the options given below:

Read the following paragraph carefully and answer the given questions.
Certain types of leukocytes (WBC) of our body like polymorpho-nuclear leukocytes (PMNL-neutrophils) and monocytes and natural killer (type of lymphocytes) in the blood as well as macrophages in tissues can phagocytose and destroy microbes. For determining the cause of allergy, the patient is exposed to or injected with very small doses of possible allergens, and the reactions studied. The use of drugs like anti-histamine, adrenalin and steroids quickly reduce the symptoms of allergy. Heroin, commonly called smack is chemically diacetylmorphine which is a white, odourless, bitter crystalline compound. This is obtained by acetylation of morphine. Techniques like radiography (use of X-rays), CT (computed tomography) and MRI (magnetic resonance imaging) are very useful to detect cancers of the internal organs. Different species of Plasmodium (P. vivax, P. malaria and P. falciparum) are responsible for different types of malaria. Of these, malignant malaria caused by Plasmodium falciparum is the most serious one and can even be fatal.
Which of the following technique is not very useful to detect the cancers of internal organs?

What is the total energy of electron in the \( n^{th} \) stationary orbit of hydrogen atom ?

If \(x\) is real, the minimum value of \(x^2-8 x+20\) is :