Tag: resistance and temperature

Questions Related to resistance and temperature

A solid reflects incident light and its electrical conductivity decreases with temperature. The bonding in this solid is :

physics optoelectronic devices resistance and temperature

  1. ionic

  2. covalent

  3. metallic

  4. molecular

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Correct Option: C
Explanation:

Metals reflect incident light by the vibrations of free electrons under the influence of electric field of incident wave. The conductivity of metals decreases with increase of temperature due to increase in random motion of free electrons. The bonding is therefore metallic.

LEDs are better than conventional incandescent power lamps because:

physics optoelectronic devices resistance and temperature

  1. LEDs have higher efficiency.

  2. LEDs look beautiful.

  3. LEDs are cheap.

  4. all of the above.

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Correct Option: D
Explanation:

LEDs are better than conventional incandescent power lamps because:-

i)LEDs use less power (watts) per unit of light generated (lumens)
ii) LEDs have higher effiiciency.
iii)LEDs have longer lifetime.
iv)LEDs are cheap.
v)LEDs look beautiful.
Hence option D is correct.

A laser device produces amplification in the

physics optoelectronic devices resistance and temperature

  1. Microwave region

  2. Ultraviolet or visible region

  3. Infrared region

  4. None of the above

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Correct Option: B
Explanation:

A laser device produces amplification in the Ultraviolet or visible region of the spectrum. 

LASER is an acronym for light amplification by.

physics optoelectronic devices resistance and temperature

  1. Stimulated energetic radiation

  2. Spontaneous emission of radiation

  3. Stimulated emission of radiation

  4. Spontaneous emission of radio waves

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Correct Option: C
Explanation:

A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term "laser" originated as an acronym for "light amplification by stimulated emission of radiation".