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Physics

Q.21) Suitable impurities are added to a semiconductor depending on its use. This is done in order to

(A) increase its life

(B) enable it to withstand higher voltages

(C) increase its electrical conductivity

(D) increase its electrical resistivity

Q.22) Of the following natural phenomena, tell which one known in Sanskrit as 'deer's thirst'?

(A) Rainbow

(B) Earthshine

(C) Halo

(D) Mirage

Q.23) One thousand microns is equal to

(A) 10-3m

(B) 10-6m

(C) 10-9m

(D) 10-12m

Q.24) Sound travels at the fastest speed in

(A) steel

(B) water

(C) air

(D) vacuum

Q.25) Superconductors are substances which

(A) conduct electricity at low temperature

(B) offer high resistance to the flow of current

(C) offer no resistance to the flow of electricity

(D) conduct electricity at high temperatures

Q.26) Light travels at the fastest speed in

(A) glass

(B) water

(C) hydrogen

(D) vacuum

Q.27) Optical fibre works on the

(A) principle of refraction

(B) total internal reflection

(C) scattering

(D) interference

Q.28) Light from the star, Alpha Centauri, which is nearest to the earth after the sun, reaches the earth in

(A) 4.2 seconds

(B) 42 seconds

(C) 4.2 years

(D) 42 years

Q.29) Radio telescopes are better than optical telescopes because

(A) they can detect faint galaxies which no optical telescope can

(B) they can work even in cloudy conditions

(C) they can work during the day and night

(D) All of the above

Q.30) Light Emitting Diodes (LED) is used in fancy electronic devices such as toys emit

(A) X-rays

(B) ultraviolet light

(C) visible light

(D) radio waves

ਜੇਕਰ ਤੁਸੀ ਕਿਸੇ ਵੀ ਸਰਕਾਰੀ ਨੌਕਰੀ ਬਾਰੇ ਜਾਣਕਾਰੀ ਲੈਣਾ ਚਾਹੁੰਦੇ ਹੋ ਤਾ ਉੱਤੇ ਦਿੱਤੇ ਕੰਮੈਟ ਬਾਕਸ ਵਿੱਚ ਕੰਮੈਟ ਕਰ ਸਕਦੇ ਹੋ ਧੰਨਵਾਦ ਅਰਨ ਮਨੀ ਜੋਬਜ ਟੀਮ