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प्रश्न
Which type of mirror has:
negative focal length?
उत्तर
concave mirror has a negative focal length because the focus of a concave mirror is in front of the mirror and on the left side.
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संबंधित प्रश्न
Analyse the following observation table showing variation of image distance (v) with object distance (u) in case of a convex lens and answer the questions that follow, without doing any calculations:
| S. No. | Object distance u(cm) | Image distance v(cm) |
| 1 | −90 | +18 |
| 2 | −60 | +20 |
| 3 | −30 | +30 |
| 4 | −20 | +60 |
| 5 | −18 | +90 |
| 6 | −10 | +100 |
(a) What is the focal length of the convex lens? Give reason in support of your answer.
(b) Write the serial number of that observation which is not correct. How did you arrive at this conclusion?
(c) Take an appropriate scale to draw ray diagram for the observation at S. No. 4 and find the approximate value of magnification.
If the image formed by a spherical mirror for all positions of the object placed in front of it is always erect and diminished, what type of mirror is it? Draw a labelled ray diagram to support your answer.
Describe with a suitable diagram, how a convex mirror diverges a parallel beam of light rays. Mark clearly the pole, focus and centre of curvature of concave mirror in this diagram.
An object is placed at a long distance in front of a convex mirror of radius of curvature 30 cm. State the position of its image.
Name the mirror which can give:
an erect and diminished image of an object.
Where would the image be formed by a convex mirror if the object is placed:
at infinity?
Draw labelled ray-diagrams to show the formation of image in both the case.
A shop security mirror 5.0 m from certain items displayed in the shop produces on-tenth magnification.
What is the radius of curvature of the mirror?
Light travels in the same straight line path while passing through different media.
To determine the focal length of a convex lens by obtaining a sharp image of a distant object we generally follow the following steps which are not in proper sequence.
(a) Hold the lens between the object and the screen
(B) Measure the distance between the lens and the screen
(C) Select a well lit distant object
(D) Place a screen opposite to the object on the lab table
(e) Adjust the position of the lens to form a sharp image
The correct sequence of these steps is:
(A) c, a, d, e, b
(B) c, d, a, e, b
(C) c, d, e, a, b
(D) c, a, e, d, b
State whether true or false. If false, correct the statement.
The convex mirror always produces a virtual, diminished and erect image of the object.
