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Recent questions tagged class12

The below reaction is known as

asked Feb 27, 2014 by sreemathi.v

1 answer

The fries rearrangement of the below reaction ,the P is

asked Feb 27, 2014 by sreemathi.v

1 answer

Infrared radiation is detected by

asked Feb 26, 2014 by thanvigandhi_1

1 answer

The electromagnetic waves that stimulate blood circulation are

asked Feb 26, 2014 by thanvigandhi_1

1 answer

The oscillating electric & magnetic vectors of an electromagnetic wave are oriented along

asked Feb 26, 2014 by thanvigandhi_1

1 answer

$UHF$ range if electromagnetic waves can be propagated by means of

asked Feb 26, 2014 by thanvigandhi_1

1 answer

Electromagnetic waves are produced by:

asked Feb 26, 2014 by thanvigandhi_1

1 answer

The pressure exerted by an electromagnetic wave of intensity $I$ on a non-reflecting surface is ($c$ is velocity of light)

asked Feb 26, 2014 by thanvigandhi_1

1 answer

The amplitude of the magnetic field part of a harmonic electromagnetic wave in vacuum is $B_o = 510\: nT$. What is the amplitude o the electric field part of the wave?

asked Feb 26, 2014 by thanvigandhi_1

1 answer

Calculate wavelength of emitted characteristic X-ray from a tungsten (Z=74) target when an electron drops from an M shell to a vacancy in K shell

asked Feb 26, 2014 by yamini.v

1 answer

Consider a hypothitical hydrogen -like atom . The wavelength in A for spectrical lines for transitions from n=P to n=1 are given by $\;\lambda=\large\frac{1500P^2}{P^2-1}\;$ where P=2 , 3 ,4,----. Then wavelength of least energetic and most energetic photons in this series .

asked Feb 26, 2014 by yamini.v

1 answer

Which one of the following reagents is used in the below reaction?

asked Feb 26, 2014 by sreemathi.v

1 answer

The claisen rearrangement of the below reaction the product is

asked Feb 26, 2014 by sreemathi.v

1 answer

What would be the major product in the following reaction?

asked Feb 26, 2014 by sreemathi.v

1 answer

A particle of charge equal to that of an electron e , and mass 208 times the mass of electron (called $\;\mu-\;$ meson ) moves in a circular orbit around a nucleus of charge +3e . (Take the mass of nucleus to be infinite ) . Then radius of $n^{th}\;$ Bohr orbit is . Find wavelength of radiation emitted when $\;mu\;$- meson jumps from third orbit to first orbit

asked Feb 26, 2014 by yamini.v

1 answer

In the following compounds the order of acid strength is

asked Feb 26, 2014 by sreemathi.v

1 answer

A particle of charge equal to that of an electron e , and mass 208 times the mass of electron (called $\;\mu-\;$ meson ) moves in a circular orbit around a nucleus of charge +3e . (Take the mass of nucleus to be infinite ) . Then radius of $n^{th}\;$ Bohr orbit is . Find the value of n for which radius of orbit is approximately the same as that of first Bohr orbit for hydrogen atom.

asked Feb 26, 2014 by yamini.v

1 answer

Which of the following statement is correct?

asked Feb 26, 2014 by sreemathi.v

1 answer

In the below reaction the products A and B are

asked Feb 26, 2014 by sreemathi.v

1 answer

Phenols can be prepared by

asked Feb 26, 2014 by sreemathi.v

1 answer

In the following reaction :The structure of the major product X is

asked Feb 26, 2014 by sreemathi.v

1 answer

A particle of charge equal to that of an electron e , and mass 208 times the mass of electron (called $\;\mu-\;$ meson ) moves in a circular orbit around a nucleus of charge +3e . (Take the mass of nucleus to be infinite ) . Then radius of $n^{th}\;$ Bohr orbit is

asked Feb 26, 2014 by yamini.v

1 answer

An ester (A) with molecular formula $C_9H_{10}O_2$ was treated with excess of $CH_3MgBr$ and the compound so formed was treated with conc.$H_2SO_4$ to form olefin (B).Ozonolysis of B gave ketone with formula $C_8H_8O$ which shows iodoform test positive.The structure of A is

asked Feb 26, 2014 by sreemathi.v

1 answer

Given: $CH_3COCH_3$ $\large\xrightarrow[\quad pyrolysis \quad]{700^{\large\circ}C}$ $A$ $\large\xrightarrow {CH_3COOH}$ $B$ $\large\xrightarrow {RCOOH} C$ based on these reactions. Write the structures of A and C

asked Feb 26, 2014 by sreemathi.v

1 answer

A moving hydrogen atom makes a head-on in elastic collision with a stationary hydrogen atom. Before collision both atoms are in ground state and after collision they move together. What is minimum velocity of moving hydrogen atom ignore of atoms is to be given the minimum excitation energy after the collision ?

asked Feb 26, 2014 by yamini.v

1 answer

Refer the below reaction:Compound F gives positive Schiff's test but (E) does not.Give structures of A and F

asked Feb 26, 2014 by sreemathi.v

1 answer

A doubly ionized lithium atom is hydrogen like atomic number $Z=3$ . Find the wavelength of radiation required to excite electron in $\;Li^{+2}\;$ from first to third Bohr orbit . Given the ionization energy of hydrogen atom as $\;13.6 eV\;.\;$

asked Feb 26, 2014 by yamini.v

1 answer

An organic acid ($X$) has molecular formula $C_8H_{16}O_2$ $X$ on heating with $NH_3$ forms $Y$ which on treatment with alkaline $Br_2$ forms $Z$.$Z$ on treatment with $HNO_2$ followed by heating with $H_2SO_4$ gives $2$,$4$-dimethyl-$2$-pentene.What are the structures of $X$ and $Z$?

asked Feb 26, 2014 by sreemathi.v

1 answer

Which of the following carboxylic acid under goes decarboxylation easily?

asked Feb 26, 2014 by sreemathi.v

1 answer

Which of the following statements is correct?

asked Feb 26, 2014 by sreemathi.v

1 answer

In an ore containing uranium , the ratio of $\;U^{238}\;$ to $\;Pb^{206}\;$ nuclei is $3$ . Then calculate age of ore assuming that all lead present in ore is final stable products of $\;U^{238}\;$ . Take half life if $\;U^{238}\;$ to be $\;4.5 \times 10^{9}\;$years

asked Feb 26, 2014 by yamini.v

1 answer

The major product obtained on heating $\gamma$-hydroxy acid $CH_3-CH_2-CHOH-CH_2-CH_2-COOH$ is

asked Feb 26, 2014 by sreemathi.v

1 answer

A tritium gas target is bombareled with a beam of mono-energetic protons of K.E 3MeV . What is K.E of neutrons emitted at an angle $\;30^{0}\;$ with incident beam ? \[\] Atomic masses are $\;H^{1}=1.007276 amu$ \[\] $\;m^{1}=1.008665 amu$\[\] $\;H_{1}^{3}=3.06056 amu$\[\] and $\;He^{2}=3.016030 amu$

asked Feb 26, 2014 by yamini.v

1 answer

In the below sequence X and Y are

asked Feb 26, 2014 by sreemathi.v

1 answer

A small quantity of solution containing $\;Na^{24}\;$ radio nuclide (Half life 15 hours ) of activity 1 micronuclids is injected into blood of a person A sample of blood of volume $\;1 cm^{3}\;$ taken after 5 hours sheemes on activity of 296 disintegration per minute. The total volume of blood in body of person is (Assume that radioactive solution mixes uniformly in blood of person . $\;(1 Ci =3.7\times10^{10} dps)$)

asked Feb 26, 2014 by yamini.v

1 answer

Which of the following compound observed in the mechanism of Beckmann rearrangement of the below

asked Feb 26, 2014 by sreemathi.v

1 answer

Light quanta with an energy 4.9 eV ejects photoelectrons from a metal with work function 4.5 eV .Then the maximum impulse transimitted to surface of metal when each electron flies out. Then de-Broglie wavelength of photoelctrons :

asked Feb 26, 2014 by yamini.v

1 answer

The correct acid strength order of the compounds

asked Feb 26, 2014 by sreemathi.v

1 answer

The treatment of $LiAlH_4$ with the below one leads to

asked Feb 26, 2014 by sreemathi.v

1 answer

$S.I$. unit of inductance i.e, henry can be written as Weber divided by

asked Feb 25, 2014 by thanvigandhi_1

1 answer

If $ V_x , V_m\: and\: V_r$ respectively are the speed of X-rays, microwaves and radio waves in air, then

asked Feb 25, 2014 by thanvigandhi_1

1 answer

In an electromagnetic wave travelling in air, the amplitude $E_o$ and $B_o$ of the electric and magnetic fields are related as (here $c$ is the speed of the wave in air)

asked Feb 25, 2014 by thanvigandhi_1

1 answer

The speed of electromagnetic waves in vacuum is given by

asked Feb 25, 2014 by thanvigandhi_1

1 answer

A laser beam is used for carrying out surgery because it

asked Feb 25, 2014 by thanvigandhi_1

1 answer

For television broadcasting, the frequency employed is normally

asked Feb 25, 2014 by thanvigandhi_1

1 answer

Long distance short-wave radio broadcasting uses

asked Feb 25, 2014 by thanvigandhi_1

1 answer

The process of superimposing signal frequency (i.e, audio wave) on the carrier wave is known as

asked Feb 25, 2014 by thanvigandhi_1

1 answer

The attenuation in optical fibre is mainly due to

asked Feb 25, 2014 by thanvigandhi_1

1 answer

Laser beams are used to measure long distances because:

asked Feb 25, 2014 by thanvigandhi_1

1 answer

The maximum distance up to which TV transmission from a TV tower of height h can be received is

asked Feb 25, 2014 by thanvigandhi_1

1 answer

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