Home
Class 12
PHYSICS
A plane mirror of circular shape with ra...

A plane mirror of circular shape with radius`r=20cm`is fixed to the ceiling .A bulb is to be placed on the axis of the mirror.A circular area fo radius`R=1m`on the floor is to be illuminated after reflection of fight from the mirror.Teh height of the room is`3m`What is maximum distance fromt he center of the mirror and the bulb so that the required area is illuminated?

Text Solution

Verified by Experts

The correct Answer is:
`75cm`
`tantheta=(r)/(h)=(R )/(3+h)`

`(0.20)/(h)=(1)/(3+h)rArr0.6+0.2h=h`
`0.8h=0.6rArrh=(3)/(4)m`
`h=75cm`
Doubtnut Promotions Banner Mobile Dark
|

Similar Questions

Explore conceptually related problems

A convex lens of focal length 15cm and a concave mirror of focal length 30cm are kept with their optic axes PQ and Rs parallel but separated in vertical directions by 0.6cm as shown .the distance between the lens and mirror is 30cm An upright object AB of height 1.2cm is placed on the optic axis PQ of the lens at the distance of 20cm from the lens.If AB is the image after refraction from the lens and reflection from the mirror ,find the distance AB from the pole of the mirror ,and obtain its magnification .Also locate positions of AB with respect to the optic axis RS

A convex lens of focal length 15 cm and a concave mirror of focal length 30 cm are kept with their optic axis PQ and RS parallel but separated in vertical directiion by 0.6 cm as shown . The distance between the lens and mirror is 30 cm . An upright object AB of height 1.2 cm is placed on the optic axis PQ of the lens at a distance of 20 cm from the lens . if A'B' is the image after refraction from the lens and the reflectiion from the mirror , find the distance of A'B' from the pole of the mirror and obtain its magnification . Also locate positions of A' and B' with respect to the optic axis RS.

Knowledge Check

  • A small plane mirror placed at the centre of a spherical screen of radius R. A beam of light is falling on the mirror, If the mirror makes n revolution per second, the speed of light on the screen after reflection from the mirror will be

    A
    `4pinR`
    B
    `2pinR`
    C
    `(nR)/(2pi)`
    D
    `(nR)/(4pi)`

  • A light ray travelling parallel to the principal axis of a concave mirror strikes the mirror at angle of incidence theta . If radius of curvature is R , then after reflection, the ray meets the principal axis at a distance d from the centre of curvature then d is

    A
    `(R)/(2)`
    B
    `(Rcostheta)/(2)`
    C
    `(R)/(2costheta)`
    D
    `(R)/(2)(1+costheta)`

  • An object kept on the principle axis is moving in the same direction as that of mirror is 10m//s and 40//13m//s . Radius of the curvature of the mirror is 20 cm. What should be the distance of object from the mirror at this instant so that the image is stationary?

    A
    45 cm
    B
    37.5 cm
    C
    25 cm
    D
    15 cm

    • Similar Questions

    Explore conceptually related problems

    A point istropic light source of power P = 12 watt is located on the axis of a circular mirror plate of radius R = 3cm. If distance of source from the plate is alpha = 39 cm and reflection coefficient of mirror plate is alpha = 0.70, calcualte force exerted by light rays on the plate.

    A convex lens of focal length 15cm and a concave mirror of focal length 30cm are kept with their optic axes PQ and RS paralledl but separated in vertical direction by 0.6 cm as shown in Figure. The distance between the lens and mirror is 30cm. An upright object Ab of height 1.2 cm is placed on the optics axis PQ of the lens at a distance of 20 cm from the lens. If A^(')B^(') is the image after refraction from the lens and reflection from the mirror, find the distance of A^(')B^(') from the pole of the mirror and obtain its magnification. Also, locate positions of A^(') and B^(') with respect to the optic axis RS.

    What will be the height of image when an object of 2 mm is placed on the axis of a convex mirror at a distance 20 cm of radius of curvature 40 cm

    A concave mirror of radius of curvature R has a circular outline of radius r. A circular disc is to be placed normal to the axis at the focus so that it collects all the light that is reflected from the mirror from a beam parallel to the axis. For r gt gt R , the area of this disc has to be at least

    A lamp is hanging along the axis of a circular table of radius r. At what height should the lamp be placed above the table, so that the illuminance at the edge of the table is (1)/(8) of that at its center

    Home
    Profile