Subject

Physics

Class

ICSE Class 12

Pre Boards

Practice to excel and get familiar with the paper pattern and the type of questions. Check you answers with answer keys provided.

Sample Papers

Download the PDF Sample Papers Free for off line practice and view the Solutions online.
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 Multiple Choice QuestionsShort Answer Type

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11. Show that S.I. unit of illuminance lux is equal to lumen/meter2 .


Illuminance is the luminous flux incident normally on unit area of the surface,

   E = straight ϕ over straight A = Lumen/ m2 

One lux is the illuminance on the inside of a sphere one metre at the centre of which a source of 1 C.P. is held.

Lux = Lumen/m2



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12. Light is incident on a block of glass at the polarizing angle. How does this polarising angle vary with the wavelength of light ?
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13. Fraunhoffer diffraction from a single slit of width 1.24 x 10-6 m is observed with light of wavelength 6200 Å. Calculate the angular width of the central maximum
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14. Refractive index of the material of a concave lens is p. The lens is immersed in a medium of refractive index μ1 (μ1 > μ) . A parallel beam of light is incident on the lens. Draw a diagram to show the path of emergent rays.
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15. For an achromatic combination of lenses in contact, why should the lenses be of opposite nature ?
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16. An electron and a proton possess the same kinetic energy. Which of the two has greater de-Broglie wavelength ? Write down the formula used.
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17. How will you increase the penetrating power of X-rays produced in an X-ray tube ?
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18. The half-life of radon is 3.8 days. Calculate the amount of radon left undecayed in a sample containing 1024 mg of radon after 38 days.
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19. The energy of an electron in the first Bhor orbit of an atom is -27.2 eV. What will be the energy in the third orbit ?
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20. Explain why the electrical conductivity of a pure semiconductor increases on heating.
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