a student focused the image of the candle flame on a white screen using a convex lens .He noted down the positions of the candle flame , screen and the lens as given below

position of candle flame = 12 cm

position of the lens= 50 cm

position of the screen = 88cm

Q 1 find the focal length of the convex lens.

Q 2 Find the position of the image of the candle flame if it is shifted towards the lens at a position of 31cm

Q3 State the nature of the image formned if the candle flame is further shifetd towards the lens..

this is a 10th board question n i m nt able 2 solve it plz helppppp

  • 11

A1) u=-(50-12) cm =-38 cm

& v=(88-50) cm=38 cm

using lens formula

1/v -1/u=1/f

1/38 -(-1/38)=1/f


f=19 cm

2) now 

u=-(50-31) cm=-19 cm





3) Now if candle is moved towards

lens the image will be magnified & 

virtual & erect

Hii im in 10th i am not a parent &

i also hav questions

hey can we discuss Science &

SST on gmail

my id is



  • 101

have  u taken a refernce point as 50 cm the lens..

  • 0

 we cant disscuss becoz i dont hav sst Question paper bt i hav the sc Q paper u can ask mee in this  only

  • -12
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