CBSE 2015,18 Light Reflection and Refraction
Answers
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➡The bouncing back of light when it's strike on any surface is called reflection
➡the changing path of light when it's go to one different medium to another is called refraction of light
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Answer:
Explanation:
Previous Years' Questions - Practical
1 Mark Questions
1. A student obtains a sharp image of the distant window (?) of the school laboratory on the screen (?) using the given concave mirror (?) to determine its focal length. Which of the following distances should he measure to get the focal length of the mirror?
??
??
??
??−?? [CBSE, 2015]
2. A student used a device (?) to obtain/focus the image of a well illuminated distant building on a screen (?) as shown below in the diagram. Select the correct statement about the device (?).
This device is a concave lens of focal length 8 ??.
This device is a convex mirror of focal length 8 ??.
This device is a convex lens of focal length 4 ??.
This device is a convex lens of focal length 8 ??. [CBSE, 2015]
3. A student traces the path of a ray of light through a rectangular glass slab for the different values of angle of incidence. He observes all possible precautions at each step of the experiment. At the end of the experiment, on analyzing the measurements, which of the following conclusions is he likely to draw?
∠?=∠?<∠?
∠?<∠?<∠?
∠?>∠?>∠?
∠?=∠?>∠? [CBSE, 2015]
4. To determine the approximate value of the focal length of a given concave mirror, you focus the image of a distant object formed by the mirror on a screen. The image obtained on the screen, as compared to the object is always :
Laterally inverted and diminished
Inverted and diminished
Erect and diminished
Erect and highly diminished [CBSE,2016]
5. Suppose you have focused on a screen the image of candle flame placed at the farthest end of the laboratory table using a convex lens. If your teacher suggests you to focus the parallel rays of the sun, reaching your laboratory table, on the same screen, what you are expected to do is to move the :
lens slightly towards the screen
lens slightly away from the screen
lens slightly towards the sun
lens and screen both towards the sun [CBSE, 2016]
6. In your laboratory, you trace the path of light rays through a glass slab for different values of angle of incidence (∠?) and in each case measure the values of the corresponding angle of refraction (∠?) and angle of emergence (∠?). On the basis of your observations your correct conclusion is :
∠? is more than ∠?, but nearly equal to ∠?
∠? is less than ∠?, but nearly equal to ∠?
∠? is more than ∠?, but nearly equal to ∠?
∠? is less than ∠?, but nearly equal to ∠? [CBSE, 2016]
7. Study the given ray diagrams and select the correct statement from the following :
Device ? is a concave mirror and device ? is a convex lens, whose focal lengths are 20 ?? and 25 ?? respectively.
Device ? is a convex lens and device ? is a concave mirror, whose focal lengths are 10 ?? and 25 ?? respectively.
Device ? is a concave lens and device ? is a convex mirror, whose focal lengths are 20 ?? and 25 ?? respectively.
Device ? is a convex lens and device ? is a concave mirror, whose focal lengths are 20 ?? and 25 ?? respectively. [CBSE, 2017]
8. A student obtains a blurred image of a distant object on a screen using a convex lens. To obtain a distinct image on the screen he should move the lens
away from the screen
towards the screen
to a position very far away from the screen
either towards or away from the screen depending upon the position of the object. [CBSE, 2017]
9. A student very cautiously traces the path of a ray through a glass slab for different values of the angle of incidence (∠?). He then measures the corresponding values of the angle of refraction (∠?) and the angle of emergence (∠?) for every value of the angle of incidence. On analysing these measurements of angles, his conclusion would be
∠?>∠?>∠?
∠?=∠?>∠?
∠?<∠?<∠?
∠?=∠?<∠? [CBSE, 2017]
2 Marks Questions:
1. A 4 ?? tall object is placed on the principal axis of a convex lens. The distance of the object form the optical centre of the lens is 12 ?? and its sharp image is formed at a distance of 24 ?? from it on a screen on the other side of the lens. If the object is now moved a little away from the lens, in which way (towards the lens or away from the lens) will he have to move the screen to get a sharp image of the object on it again? How will the magnification of the image be affected? [CBSE, 2015]
2. An object of height 2.5 ?? is placed at a distance of 15 ?? from the optical centre ‘?’ of a convex lens of focal length 10 ??. Draw a ray diagram to find the position and size of the image formed. Mark optical centre ‘?’, principal focus ? and height of the image on the diagram. [CBSE, 2016]