A concave mirror gives an image three times as large as the object placed at a distance of 20 cm from it. For the image to be real, the focal length should beA. 10 cmB. 15 cmC. 20 cmD. 30 cm

A concave mirror gives an image three times as large as the object pla

1.	A concave mirror gives an image three times as large as the object placed at a distance of 20 cm from it. For the image to be real, the focal length should beA. 10 cmB. 15 cmC. 20 cmD. 30 cm
Answer» Correct Answer - B (b) Magnification, `m=(f)/(f-u) rArr -3=(f)/(f-(-20))` `rArr` The focal length of mirror, f=-15 cm

Discussion

No Comment Found

Related InterviewSolutions

An infinitely long rod lies along the axis of a concave mirror of focal length f. The near end of the rod is distance `u gt f` from the mirror. Its image will have lengthA. `(uf)/(u-f)`B. `(uf)/(u+f)`C. `(f^(2))/(u+f)`D. `(f^(2))/(u-f)`
An infinitely long rod lies along the axis of a concave mirror of focal length f. The near end of the rod is distance `u gt f` from the mirror. Its image will have lengthA. `f^(2)/(u-f)`B. `(uf)/(u-f)`C. `f^(2)/(u+f)`D. `(uf)/(u+f)`
An infinity long rod lies along the axis of a concave mirrror of focal length f.The near end of a the rod is at a distance `ugtf`from the mirror ,Its image will have a length:A. `(f^(2))/(u-f)`B. `(uf)/(u-f)`C. `(f^(2))/(u+f)`D. `(uf)/(u+f)`
STATEMENT-`1`A real object is kept on pricipal axis of mirror.Size of image measured is equal to size of object.The mirror must be plane mirror. `STATEMENT 2` For a plane mirrror magnification is unity.A. STATEMENT -`1`is true statement `2` is true,Statement -`2`is a correct explanation for statement -`1`B. STATEMENT -`1`is true statement `2` is true,Statement -`2`is a not a correct explanation for statement -`1`C. Statement -`1`is true,Statement -`2`is FalseD. Statement -`1`is False ,Statement -`2`is True
In the figure shown,the image of a real object is formed at point I.AB is theprincipal axis of the mirror ,The mirrror must be: A. concave & placed towards right `I`B. concave & placed towards left of `I`C. convex & placed towards right of`I`D. convex & placed towards left`I`
In the figureshownm the image of a real object is formed at point I. AB is the principal axis of the mirror. The mirror must be A. concave and placed towards right of IB. concave and placed towards left of IC. convex and placed towards right of ID. Convex and placed twowards left of I
If `._(i)mu_(j)` represents refractive index when a light ray goes from mefium `i` to medium `j`, then the product `._(2)mu_(1)xx._(3)mu_(2)xx._(4)mu_(3)` is equal toA. `._(3)mu_(1)`B. `._(3) mu_(2)`C. `1/(._(1)mu_(4))`D. `._(4)mu_(2)`
Statement-1 : it is impossible to photograph a virtual image. Statement-2 : The rays which appear diverging from a virtual image fall on the camera and a real image is captured.A. If both assertion and reason are true and the reason is the correct explanation of the assertionB. If both assertion and reason are true but reason is not the correct explanation of the assertionC. If assertion is true but reason is falseD. If assertion is f alse but reason is true
The number of images formed by two plane mirrors inclined at `60^@` of an object placed symmetrically between mirror isA. 6B. 2C. 5D. 4
A man holding a lighted candle in front of a thick glass mirror and viewing it obliquely sees a number of images of the candle. What is the origin of these multiple images ?

A concave mirror gives an image three times as large as the object placed at a distance of 20 cm from it. For the image to be real, the focal length should beA. 10 cmB. 15 cmC. 20 cmD. 30 cm

Discussion

No Comment Found

Related InterviewSolutions

Reply to Comment