Two metals A and B have work functions 4 eV and 6 eV respectivel

Subject

Physics

Class

ICSE Class 12

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 Multiple Choice QuestionsShort Answer Type

11.

To which regions of the EM spectrum do the following wavelengths belong:

a) 250 nm
b) 1500 nm


12.

What is the difference between polarised light and unpolarized light?


13.

Name the principle on the basis of which optical fibres work?


14.

Calculate dispersive power of a transparent material given by:

nv = 1.56, nr = 1.54, ny= 1.55


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15.

What is meant by short-sightedness?


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16.

Two metals A and B have work functions 4 eV and 6 eV respectively. Which metal has lower threshold wavelength for photoelectric effect.


Work function of A = 4 eV
Work function of B = 6 eV

Let, W be the work function, h be the Planck constant and straight nu subscript straight o the threshold frequency.

We know that,

straight W space equals space hC over straight lambda subscript straight o
straight lambda subscript straight o space equals space hC over straight W
straight lambda space proportional to space 1 over straight W

Hence, metal B have lower threshold wavelength because work function is inversely proportional to wavelength.


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17.

Calculate angular momentum of an electron in the third Bohr orbit of hydrogen atom.


18.

In a nuclear reactor, what is the function of a moderator?


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19.

In our nature, where is the nuclear fusion reaction taking place continuously?


20.

What is the use of a Zener diode?


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