Subject: Science, asked on 18/3/18

## i asked if v and u are unknown then how will u find them ? the focal length is given and m is also given .. then how will u find u and v plzzz don t say the mirror or lens formula or m=v/u or 0v/u. i need the formula for both lens and mirror .. the formula that be like m=f/f-u  like that i need for lens and mirror and also finding v like m=f-v/f i don t know the correct formula plzzz tell me the correct ans

Subject: Science, asked on 18/3/18

## how to find u and v where f is known and m is also known i need the formula tomorrow is sci exam plzzz help ... i need it for both lens and mirror

Subject: Science, asked on 17/3/18

## If an incident ray falls normally on a glass slab, then what will be the angle of incidence and angle of refraction?

Subject: Science, asked on 17/3/18

## how to find f where u and v are unknown? can anyone tell the formula to find

Subject: Science, asked on 16/3/18

## An object of hight 4.0 cm is placed at a distance of 30 cm from the optical centre O' of a convex lens of focal length 20 cm.Draw a ray diagram to find the position and size of the image formed.Mark optical centre O' and principal focus F' on the diagram.Also find the approximate ratio of size of the image to the size of the object.

Subject: Science, asked on 16/3/18

## What is meant by the power of the lens? A student uses a lens of focal length 40cm and another -20 cm. Write the nurture and power of each lens.

Subject: Science, asked on 16/3/18

## For this question, I drew the proper figure, found out the height of image using lens formula in rough sheet and marked the answers in the answer sheet properly. So will I get full credits? As only ray diagram is asked....I did the calculations in rough sheet...meritnation Q. An object of height 2.5 cm is placed at a distance of 15 cm from the optical centre 'O' of a convex lens of focal length 10 cm. Draw a ray diagram to find the position and size of the image formed. Mark optical centre 'O', principal focus F and height of the image on the diagram.

Subject: Science, asked on 16/3/18

## Solve this Q.12. 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 he 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?

Subject: Science, asked on 16/3/18

## a concave mirror produces three times magnified real image of an object on a screen which is placed 30cm away from object find focal length of the mirror

Subject: Science, asked on 15/3/18

## I asked this just before 5 minutes but the answer was given 1/v-1/u= 1/f but the formulae of convex mirror is 1/v+1/u=1/f 1.  A convex lens has a focal length of 10 cm. At what distance from the lens should the object be placed so that it forms a real and inverted image 20 cm. away from the lens? What would be the size of the image formed if the object is 2 cm high? With the help of a ray diagram show the formation of the image by the lens in this case?

Subject: Science, asked on 15/3/18

## While drawing ray diagrams, should we measure focal length from optical centre or boundary of lens?

Subject: Science, asked on 15/3/18

## An object is placed at a distance of one & a half focal length of a concave mirror. Find the position of the image and also find the magnification and nature of image formed

Subject: Science, asked on 15/3/18

## Q.  A student places a candle flame at distance of about 60 cm from a convex lens of focal length 10 cm and focuses the image of the flame on a screen. After that he gradually moves The flame towards the lens and each time focuses the image on the screen.  (a) In which direction towards or away from the lens, does he move the screen to focus the image?  (b) How does the size of the image change?  (c) How does the intensity of the Image change as the moves towards the Lens?  (d) Approximately for what distance between the flame And the lens. the image formed or, the screen is inverted and of the same size?

Subject: Science, asked on 15/3/18

## To find the focal length of a concave mirror in an experiment, why should the distant object be sun rather than a distant tree?

Subject: Science, asked on 15/3/18

## Can i know how to take approx values correctly, many time we get an answer like 1.66 and write 1.67.... I usually dont like taking approx values because i fear it will be called wrong. I even fear what is the examiner seeing in the answer key , the approx value or the exact value. Please help me on this.

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