A student focused the image of a candle flame on a white screen using a convex mirror . He noted down the position of candle, screen and lens under i)Position of Candle- 12.6 cm ii)Position of convex lens-51.8cm iii)Position of screen- 91.0 cm a)Calculate the focal length of the lens. b)where will the image be formed if he shifts the candle towards the lens at a position of 32.2 cm? c)What will be the nature of the image formed if he further shifts the candle towards the lens?
Answers
Answered by
15
given:
object distance=u=12.6-51.8=-39.2cm
image distance =v=91-51.8=39.2cm
by using lens formula:
1)1/f=1/v-1/u
1/f=1/39.2+1/39.2=2/39.2
therefore, f=19.6cm
2) v=?
if u=32.2-51.8=-19.6cm
f=19.6cm
1/f=1/v-1/u
1/v=1/f+1/u
1/19.6-1/19
so, V=infinity, the image will be formed at infinity as the object is kept at the focus.
3)As the object is shifted towards lens, the object distances thus decreases and so we would see a variation in image nature,the image will be virtual,erect and magnified.
object distance=u=12.6-51.8=-39.2cm
image distance =v=91-51.8=39.2cm
by using lens formula:
1)1/f=1/v-1/u
1/f=1/39.2+1/39.2=2/39.2
therefore, f=19.6cm
2) v=?
if u=32.2-51.8=-19.6cm
f=19.6cm
1/f=1/v-1/u
1/v=1/f+1/u
1/19.6-1/19
so, V=infinity, the image will be formed at infinity as the object is kept at the focus.
3)As the object is shifted towards lens, the object distances thus decreases and so we would see a variation in image nature,the image will be virtual,erect and magnified.
Answered by
4
Answer:
( i ) . Object distance u = 50 - 26 = 24 cm
Image distance v = 74 - 50 = 24 cm .
Since object distance is equal to image distance.
2 f = 24
= > f = 12 cm
So , focal length of object is 12 cm.
( ii ) . u = 50 - 38 = 12 cm
It's mean candle is at focus.
= > Image will form at infinity.
( ii ) Refer to attachment for ray diagram.
Attachments:
Similar questions