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Payal Arora
Subject: Science
, asked on 1/3/18
A concave mirror produces 3 times enlarged image of an object placed at 10cm in front of it. Calculate the focal length of the mirror
Answer
2
Trishu
Subject: Science
, asked on 1/3/18
Solve this:
Q. Given that :
${i}_{1}={r}_{2}and{r}_{1}={i}_{2}$
.
Then prove that ABE is parallel to FCD.
Answer
2
Ashmita Debnath
Subject: Science
, asked on 28/2/18
Ques 12
Q12. Rohit focused the image of a candle flame on a white screen using a convex lens. He noted down the position of the candle, screen and lens as under:
Position of candle = 26.0 cm
Position of convex lens = 50.0 cm
Position of screen = 74.0 cm
i) What is the focal length of the convex lens ?
ii) Where will the image be formed if the shifts the candle towards the lens at a position of 38 cm?
iii) Draw a ray diagram to show the formation of the image in case (ii) as said above?
Answer
1
Harsh
Subject: Science
, asked on 28/2/18
Answer question 4 with proper steps.
Q.4. The power of a combination of two lenses XY is 5 D if the focal length of lens X is 15 cm. State the nature and focal length of lens Y.
Answer
4
Payal Arora
Subject: Science
, asked on 28/2/18
Give the relationship of magnification with focal length of a spherical mirror
Answer
4
Nazreen
Subject: Science
, asked on 28/2/18
pls answer both the questions
Q.(b) The mirror outside the driver side of a vehicle is usually a convex mirror. Printed on such a mirror is usually the warning "Objects in the mirror are closer than they appear." What is the reason for this warning? What is the advantage of using it?
Q.(c). Give the relationship of magnification with focal length of a spherical mirror.
Answer
3
Raghav Singh
Subject: Science
, asked on 28/2/18
In this q. Everything is clear but i can't understand the last part, why 15 was subtracted? I mean how it tells that the image will coincide??please explain this part.
21. If an object is held at a distance of 60 cm from a convex mirror of focal length 20 cm. at what distance from the convex mirror, would a plane mirror be held, so that images in the two mirrors coincide?
Answer
1
Raghav Singh
Subject: Science
, asked on 28/2/18
Why the angle of reflection here is 45 degree in the answer , give reason?
Answer
1
Raghav Singh
Subject: Science
, asked on 28/2/18
Please answer this q.
Q. Does the incident and emergent ray coincide in a glass slab refraction? Give reason.
Q. A ray of light enters a diamond from air. If the refractive index of diamond is 2.42, what % (Per cent ) is speed of light in diamond with that of speed in air?
Answer
1
Raghav Singh
Subject: Science
, asked on 28/2/18
Please answer q. 47
Answer
1
Raghav Singh
Subject: Science
, asked on 28/2/18
Please explain the second part of this q.?
Q25.
HOTS
What change do you expect in the focal length of a concave mirror and a convex lens, when immersed in water?
Sol. There is no change in the focal length of concave mirror because it is about half of its radius of curvature and has nothing to do with the external medium.
However, the focal length of convex lens increase because refractive index of glass with respect to water is less than refractive index of glass with respect to air.
Answer
1
Trishu
Subject: Science
, asked on 28/2/18
Prove this mathematically....
Q. Given that :
${i}_{1}={r}_{2}and{r}_{1}={i}_{2}$
then prove that ABE is parallel to FCD.
Answer
4
Raghav Singh
Subject: Science
, asked on 28/2/18
In this how we got 25 degree 22'?
Answer
1
Trishu
Subject: Science
, asked on 27/2/18
Q. Prove that i1 = r2
Answer
2
Shrish Vaidya
Subject: Science
, asked on 27/2/18
answer 16th question. plzzzzz no links
Q.16. A student has to project a three times magnified mage of a candle flame on a wall. Name the type of the lens (converging/ diverging) required for the purpose. If the candle flame is at a distance of 6 m from the wall, find the focal length of the lens.
Answer
2
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Q. Given that : ${i}_{1}={r}_{2}and{r}_{1}={i}_{2}$.

Then prove that ABE is parallel to FCD.

Q12. Rohit focused the image of a candle flame on a white screen using a convex lens. He noted down the position of the candle, screen and lens as under:

Position of candle = 26.0 cm

Position of convex lens = 50.0 cm

Position of screen = 74.0 cm

i) What is the focal length of the convex lens ?

ii) Where will the image be formed if the shifts the candle towards the lens at a position of 38 cm?

iii) Draw a ray diagram to show the formation of the image in case (ii) as said above?

Q.4. The power of a combination of two lenses XY is 5 D if the focal length of lens X is 15 cm. State the nature and focal length of lens Y.

Q.(b) The mirror outside the driver side of a vehicle is usually a convex mirror. Printed on such a mirror is usually the warning "Objects in the mirror are closer than they appear." What is the reason for this warning? What is the advantage of using it?

Q.(c). Give the relationship of magnification with focal length of a spherical mirror.

21. If an object is held at a distance of 60 cm from a convex mirror of focal length 20 cm. at what distance from the convex mirror, would a plane mirror be held, so that images in the two mirrors coincide?

Q. Does the incident and emergent ray coincide in a glass slab refraction? Give reason.

Q. A ray of light enters a diamond from air. If the refractive index of diamond is 2.42, what % (Per cent ) is speed of light in diamond with that of speed in air?

Q25.

HOTSWhat change do you expect in the focal length of a concave mirror and a convex lens, when immersed in water?Sol. There is no change in the focal length of concave mirror because it is about half of its radius of curvature and has nothing to do with the external medium.

However, the focal length of convex lens increase because refractive index of glass with respect to water is less than refractive index of glass with respect to air.

Q. Given that : ${i}_{1}={r}_{2}and{r}_{1}={i}_{2}$

then prove that ABE is parallel to FCD.

Q.16. A student has to project a three times magnified mage of a candle flame on a wall. Name the type of the lens (converging/ diverging) required for the purpose. If the candle flame is at a distance of 6 m from the wall, find the focal length of the lens.