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A battery operated tourch is adjusted to...

A battery operated tourch is adjusted to send and almost parallel beam of light. It produces an illuminance of 40 lux when the light falls on a wal 2m away. The illuminance produced when it fals on a wal 4 m away is close to

A

40 lux

B

20 lux

C

10 lux

D

5 lux

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The correct Answer is:
A
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HC VERMA-PHOTOMETRY-All Questions
  1. An electric bulb is hanging over a table at a height of 1 m above it. ...

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  2. Light from a point source falls on a screen. If the separation between...

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  3. A battery operated tourch is adjusted to send and almost parallel beam...

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  4. The intensity produced by a long cylindrical light source at a small d...

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  5. A photographic plate placed at a distance of 5 cm from a weak point so...

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  6. A photographic plate is placed directly in front of a small diffused s...

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  7. A point source of light moves in a straight line parallel to a plane t...

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  8. Figure shows a glowing mercury tube. The intensities at point A, B and...

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  9. The brightnes producing capacity of a source

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  10. A room illuminated by an extended source. The iluminance at a particul...

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  11. Mark the correct options

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  12. Mart out the correct options

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  13. A source emits 45 joules of energy in 15 s. What is the radiant flux o...

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  14. A photographic plate records sufficient intense lines when it is expos...

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  15. Using figure 22.1, find the relative luminosity of wavelength (a) 480 ...

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  16. The relative luminosity of wavelength 600 nm is 0.6. Find the radiant ...

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  17. The luminous flux of a monochromatic source of 1 W is 450 lumen W^-1. ...

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  18. A source emits light of wavelengths 555 nm and 600 nm. The radiant flu...

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  19. A light source emits monochromatic light of wavelength 555 nm. The sou...

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  20. A source emits 31.4 W of radiant flux distributed uniformly in all dir...

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