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Two light sources of intensities 8 cd an...

Two light sources of intensities 8 cd and 12 cd are placed on the same side of a photometer screen at a distance of 40 cm from it. Where should a 80 cd source be placed to balance the illuminance ?

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80 cm
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SL ARORA-RAY OPTICS-Problems For Self Practice
  1. A good photographic print is obtained by an exposure of 2s at a distan...

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  2. Two lamps of illuminating powers 25 cd and 100 cd are placed at the en...

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  3. Two light sources of intensities 8 cd and 12 cd are placed on the same...

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  4. A lamp is hanging at a height of 4 m above a table. The lamp is lowere...

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  5. In Bunsen's grease spot photometer, light from a lamp with dirty chimn...

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  6. An electric bulb illuminates a plane surface. The intensity of illumin...

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  7. A lamp is hanging along the axis of a circular table of radius r. at w...

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  8. An electric bulb is hanging above the centre of a circular table of ra...

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  9. In Fig. the circular cross-section of tunnel is shown. A 100 W almp is...

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  10. A frosted bulb which may be taken as an isotropic source, gives as ill...

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  11. A man is running away from a plane mirror at the speed of 5 ms^(-1). W...

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  12. A plane mirror rotating at an angular velocity of 3 radian/s reflects ...

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  13. A ray of light is incident at an angle of 60^(@) on a horizontal plane...

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  14. rays of light strike a horizontal plane mirror at an angle of 45^(@). ...

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  15. Two plane mirrors are inclined at angle theta as shown in figure. If a...

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  16. An object 0.04 m high is placed at a distance of 0.8 m from a concave ...

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  17. Find the size, nature and position of image formed by a concave mirror...

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  18. An object is placed in front of a concave mirror of radius of curvatur...

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  19. An object is placed at a distance of 15 cm from a convex mirror and im...

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  20. A convex mirror and a concave mirror of radius 10cm each are placed 15...

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