27) Which is the most powerful oxidizing agent. a) Iodine b) fluorine c) oxygen

Question

27) Which is the most powerful oxidizing agent.

a) Iodine

b) fluorine

c) oxygen

d) lithium

.

28) Why do most materials fail?

a) Theoretical, ultimate stress is reached

b) Defects

c) Sin

d) Boston Tunnel Authority

.

29) Semiconductors are transparent in the following regions:

a) At wavelengths longer than their bandgap energy, Eg.

b) At wavelengths shorter than their bandgap energy, Eg.

c) Only at their bandgap energy, Eg.

d) They are not transparent at any wavelength

Please answer all of them without guessing!!! Thanks

Explanation / Answer

27 ) b) fluorine

reason :   fluorine is highest electro negative element in the peroidic table . so which can readily accept electron. accepting electron is nothing but oxidizing nature

28) b) Defects

in general any material having some defects in their structure. these defects may be of frankel , shottky , line edge , disslocation , metal excess and so on. we cannot get perfect meterial

29 ) b) At wavelengths shorter than their bandgap energy, Eg

explanation:

at higher energy like IR , UV , visible than Eg (that means shorter wave length) semi conductors are transparent but lower eenrgy (higher wave length ) like micro , radio waves these are opaque.

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