Question

a convex lens has a focal length of 10 cm?.at what distance from the lens is the object to be placed ? .so it forms a real and inverted image 20 cm away from the lens?what should be the sise of the image if the object is 2cm high?with help of a ray diagram show the formation of lens in this case

Answer 1

Answer:

Focal length=f=10cm

Image distance=v=20cm

Using sign convention,

f is positive, v is also positive

Lens formula,1/f=1/v-1/u

1/10=1/20–1/u

1/u=1/20–1/10

1/u=(10–20)/200

1/u=-10/200

u=-20 Object

distance=20cm

(minus indicates that the lens is converging lens)

by the way credit to this guy who already solved it i just copyed his response  

RamanarroraExpert

Answer 2

★★Question;-

✓✓A convex lens has a focal length of 10cm. At what distance from the lens should the object be placed so that it forms real and inverted image 20cm away from the lens? What would be the size of the image formed if the object is 2cm high? With the help of ray diagram show the formation of the image.

★★Given;-

• Focal length$(f)= 10cm$

• Image distance$(v)=20cm$

★★Answer;-

• Using sign convention,f is positive,v is also positive

Formula is:-

$⇢\frac{1}{f}=\frac{1}{v}-\frac{1}{u}$

$⇢\frac{1}{10}=\frac{1}{20}-\frac{1}{u}$

$⇢\frac{1}{u}=\frac{1}{20}-\frac{1}{10}$

$⇢\frac{1}{u}=\frac{(10-20)}{200}$

$⇢\frac{1}{u}=\frac{-10}{200}$

$\boxed{\boxed{{u=-20}}}$

Then,

$⇢\frac{Height\:of\:image}{Height\:of\:object}=\frac{-v}{u}$

$⇢\frac{Height\:of\:image}{2}=\frac{-20}{20}$

$\boxed{\boxed{{∴Height\:of\:image=2cm}}}$✓✓