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प्रश्न
Describe the positions of the source of light with respect to a concave mirror in Floodlight.
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उत्तर
In a floodlight, the light source is slightly beyond the radius of curvature, which gives us the right light.
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संबंधित प्रश्न
Draw the following diagram in which a ray of light is incident on a concave/convex mirror on your answer sheet. Show the path of this ray, after reflection, in each case.
A student obtained a sharp image of a candle flame placed at the distant end of the laboratory table on a screen using a concave mirror to determine its focal length. The teacher suggested him to focus a distant building, about 1 km away from the laboratory, for getting more correct value of the focal length. In order to focus the distant building on the same screen, the student should slightly move the
(a) mirror away from the screen
(b) screen away from the mirror
(c) screen towards the mirror
(d) screen towards the building
To construct a ray diagram we use two rays of light which are so chosen that it is easy to determine their directions after reflection from the mirror. Choose these two rays and state the path of these rays after reflection from a concave mirror. Use these two rays to find the nature and position of the image of an object placed at a distance of 15 cm from a concave mirror of focal length 10 cm.
A spherical mirror produces an image of magnification −1 on a screen placed at a distance of 40 cm from the mirror:
(i) Write the type of mirror.
(ii) What is the nature of the image formed?
(iii) How far is the object located from the mirror?
(iv) Draw the ray diagram to show the image formation in this case.
The radius of curvature of a spherical mirror is 20 cm. What is its focal length?
Name the mirror that can give an erect and enlarged image of an object.
We wish to obtain an erect image of an object, using a concave mirror of focal length 15 cm. What should be the range of distance of the object from the mirror? What is the nature of the image? Is the image larger or smaller than the object? Draw a ray diagram to show the image formation in this case.
Name the type of mirror used in the following situation:
Headlights of a car
Support your answer with reason.
Three students A, B and C focussed a distant building on a screen with the help of a concave mirror. To determine focal length of the concave mirror they measured the distances as given below:
Student A : From mirror to the screen
Student B : From building to the screen
Student C : From building to the mirror
Who measured the focal length correctly ;
(a) Only A
(b) Only B
(c) A and B
(d) B and C
Draw a ray diagram showing how a concave mirror can be used to produce a real, inverted and diminished image of an object.
Name the type of mirror used by dentists. How does it help?
Giving reasons, state the 'signs' (positive or negative) which can be given to the following:
(a) object distance (u) for a concave mirror or convex mirror
(b) image distance (v) for a concave mirror
(c) image distance (v) for a convex mirror
At what distance from a concave mirror focal length 10 cm should an object 2 cm long be placed in order to get an erect image 6 cm tall?
A concave mirror has a focal length of 4 cm and an object 2 cm tall is placed 9 cm away from it. Find the nature, position and size of the image formed.
A large concave mirror has a radius of curvature of 1.5 m. A person stands 10 m in front of the mirror. Where is the person's image?
A concave mirror produces a real image 1 cm tall of an object 2.5 mm tall placed 5 cm from the mirror. Find the position of the image and the focal length of the mirror.
At what distance from a concave mirror of focal length 10 cm should an object be placed so that:
- its real image is formed 20 cm from the mirror?
- its virtual image is formed 20 cm from the mirror?
What type of mirror should be used as a shaving mirror?
Which of the following are concave mirrors and which convex mirrors?
Shaving mirrors, Car headlight mirror, Searchlight mirror, Driving mirror, Dentist’s inspection mirror, Torch mirror, Staircase mirror in a double-decker bus, Make-up mirror, Solar furnace mirror, Satellite TV dish, Shop security mirror.
A concave mirror cannot be used as:
(a) a magnifying mirror
(b) a torch reflector
(c) a dentist's mirror
(d) a real view mirror
Which of the following can make a parallel beam of light from a bulb falls on it?
(a) concave mirror as well as concave lens
(b) convex mirror as well as concave lens
(c) concave mirror as well as convex lens
(d) concave mirror as well as convex lens
Draw a ray diagram to show the formation of image of an object placed on the principal axis of a convex mirror. State the position, size and nature of the image. What happens to the image as the object is moved away from the mirror?
How can a concave mirror be used to obtain a virtual image of an object? Draw a diagram to illustrate your answer.
Suppose you have three concave mirrors A, B and C of focal lengths 10 cm, 15 cm and 20 cm. For each concave mirror you perform the experiment of image formation for three values of object distance of 10 cm, 20 cm and 30 cm. Giving reason answer the following:
(a) For the three object distances, identify the mirror/mirrors which will form an image of magnification – 1.
(b) Out of the three mirrors identify the mirror which would be preferred to be used for shaving purposes/makeup.
(c) For the mirror B draw ray diagram for image formation for object distances 10 cm and 20 cm.
A student determines the focal length of a device 'X' by focusing the image of a distant object on a screen placed 20 cm from the device on the same side as the object. The device 'X' is
(a) Concave lens of focal length 10 cm
(b) Convex lens of focal length 20 cm
(c) Concave mirror of focal length 10 cm
(d) Concave mirror of focal length 20 cm
A student has focused the image of a candle flame on a white screen using a concave mirror. The situation is as given below:
Length of the flame = 1.5 cm
Distance of flame from the mirror = 18 cm
If the flame is perpendicular to the principal axis of the mirror, then calculate the following:
- Distance of the image from the mirror
- Length of the image
If the distance between the mirror and the flame is reduced to 10 cm, then what would be observed on the screen? Draw ray diagram to justify your answer for this situation.
A student obtained a sharp inverted image of a distant tree on a screen placed in front of the concave mirror. He then removed the screen and tried to look into the mirror. He would now see
(A) a very blurred image on the wall opposite to the mirror
(B) an erect and magnified image of the tree in the mirror
(C) no image as the screen has been removed
(D) a highly diminished inverted image of the tree at the focus of the mirror.
In which equipment/s do you find ___________________
Consider the following properties of virtual images:
- cannot be projected on the screen
- are formed by both concave and convex lens
- are always erect
- are always inverted
The correct properties are:
List four characteristics of the image formed by a concave mirror of focal length 40 cm when the object is placed in front of it at a distance of 20 cm from its pole.
According to cartesion sign convention, which mirror and which lens has negative focal length?
A 10 mm long awl pin is placed vertically in front of a concave mirror. A 5 mm long image of the awl pin is formed at 30 cm in front of the mirror. The focal length of this mirror is ______.
A concave mirror produces a magnification of +4. The object is placed ______.
Examine the above figure and state which of the following option is correct? [one small box in the figure is equal to 1 cm]
The focal length of a concave mirror is 5cm. Its radius of curvature is ______.
What is a concave and convex mirror?
Between which two points of a concave mirror should an object be placed to obtain a magnification of -2?
A student wants to obtain an erect image of an object using a concave mirror of 10 cm focal length. What will be the distance of the object from mirror?
A student took three concave mirrors of different focal lengths and performed the experiment to see the image formation by placing an object at different distance with these mirrors as shown in the following table.
| Case No. | Object-distance | Focal length |
| I | 45 cm | 20 cm |
| II | 30 cm | 15 cm |
| III | 20 cm | 30 cm |
Now answer the following questions:
(a) List two properties of the image formed in Case I.
(b) In which one of the cases given in the table, the mirror will form real image of same size and why?
(c) Name the type of mirror used by dentists. Given reason why do they use such type of mirrors.
OR
(c) Look at the table and identify the situation (object distance and focal length) which resembles the situation in which concave mirrors are used as shaving mirrors? Draw a ray diagram to show the image formation in this case.
