In order to determine the focal length of a concave mirror, a student obtained a sharp image of the grill of a window in the laboratory wall on a screen. His teacher suggested that to get better result for focal length, he should focus a distant tree instead of the window grill. In which direction should the mirror be moved for this purpose so as to get a sharp image of the tree on the screen?
Important Questions on Multiple Choice Questions
A student performs an experiment on finding the focal length of a convex lens by keeping a lighted candle on one end of the laboratory table, a screen on its other end and the lens between them as shown in the figure. The positions of the three are adjusted to get a sharp image of the candle flame on the screen. If now the candle flame were to be replaced by a distant lamp on a far away electric pole, the student would be able to get a sharp image of this distant lamp on the screen by moving:
Which diagram shows the formation of image correctly?
A student was given the following suggestions by his classmates for performing the experiment on finding the focal length of a convex lens :
(A) Select any object very far away from the laboratory window
(B) Select a well illuminated object far (but not very far) from the laboratory window
(C) keep all the lights of the laboratory on
(D) Place the lens between the object and the screen
(E) Place the screen between the object and the lens
(F) Obtain the sharpest image of the object on the screen
He can perform the experiment better by following the suggestions :
