Question

Object distance and image distance of a lens are - 30 cm and -

10 cm respectively. Find the magnification and decide the type

of lens used and nature of the image.​

Answer 1

Answer:

• Magnification = -1/3
• Convex lens
• Smaller than the object

Explanation:

Given:-

• Object Distance ,u = -30 cm

• Image distance ,v = 10 cm

To Find:-

• Magnification,m

Solution:-

As we know that magnification is defined as the ratio of height of image to the ratio of height of object.

• m = hi/ho = v/u

→ m = v/u

where,

• m denotes magnification
• v denotes image distance
• u denotes object distance

Substitute the value we get

→ m = 10/-30

→ m = -10/30

→ m = -1/3

Here, negative sign show the the image formed is real and Inverted. As we know that Convex lens formed real image .

and the image formed is smaller than the object.

• Hence, the magnification of the lens is -1/3 .

Answer 2

Answer:

Given :-

• Object distance = -30 cm
• Image distance = 10 cm

To Find :-

• Lens
• Nature
• Magnification

Solution :-

As we know that

$\huge \bf \red{m \: = \frac{v}{u}}$

Here,

M is the magnification

V is the Image distance

U is the object distance

$\tt \: m = \dfrac{ 10}{ - 30}$

$\tt \: m \: = \dfrac{ - 10}{30}$

Cancelling both by 10

$\tt \: m \: = \dfrac{ - 1}{3}$

Magnitude of Image is -1/3.

Convex Lens

Smaller than object