a/r solution 6

Biology:

1. A

Transmission of nerve impulse across synapse is accomplished by neurotransmitter, low molecular mass substances released in minute amounts at interneural, neuromuscular and neuroglandular junctions. Most widespread transmitter is acetylcholine

2. A

All terrestrial mammals are air breathers. Because of terrestrial habitat they have well developed lungs for air breathing.

3. C

There is no chance of transmission of malaria to man on the bite of male anopheles as their mouth parts are organised to feed on fruit juice and leaves and they cant even bite humans

4. C

Thiamin or vitamin B1 deficiency causes beri beri

5. D

Minerals take part in biological reactions and are thus biologically active. Anaemia is caused by deficiency of iron

Physics:

1. C

A laser is a highly monochromatic and nearly parallel beam of light and can be focussed with high intensity and thus can drill holes. Torch light beam disperses away and is less intense

2. C

Converging lenses can also form virtual images

3. D

4. B

As radio waves are electromagnetic waves, they can be polarised

5. A

According to Newton’s corpuscular theory of light, newton explained refraction as being due to the attraction of the light particles by the particles of the medium making light rays bend in the boundary. But, if this were the case, the velocity of light in a denser medium should have been more than that in rarer medium. But this is actually not so. The velocity of light in air is more than that in water

Chemistry:

1. A

Principal quantum number represent the name, size and energy of shell to which the electron belongs. Higher is the value of n, greater is the distance of the shell from the nucleus and hence greater is the energy

2. A

According to aufbau principle, the unfilled shell with the lowest n+1 value should be filled first. Therefore, 4s is filled prior to 3d

4s = 4+0=4

3d= 3+2=5

3. B

The ideal gas equation is PV=nRT

For a fixed number of moles, it is clear that PV=constant for constant T

4. A

In isothermal expansion, temperature is maintained constant so internal energy change is zero (^E=0)

^E=q+w q=heat w=work done so q=-w

This shows that work is done by the system at the expense of heat absorbed

5. A

Alkali metals have very low value of ionisation energy as compared to other metals. So electrons are excited with low energies, like flame and imparts colour

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