
A convex lens produces a real image m times the size of the object. What will be the distance of the object from the lens?
Answer
499.5k+ views
Hint: Use the formula for magnification due to a lens. With this find an expression for the position of the image. Then use the lens formula and substitute the value of the position of image. Hence, find the expression for the object position from the lens.
Formula used: magnification
Complete step by step answer:
It is given that a convex lens produces a real image. The size of the image produced is said to m times larger than the size of the object.
We will use the formula for magnification. The magnification is the ratio of the height of the image to the height of the image. A real image is always inverted. Therefore, the value of magnification is negative. This means that magnification is (-m).
The value of magnification is equal to , where v and u are the distances of the image and the object from the lens.
…. (i).
The relation between the position of the object and its image is given as …. (ii), where f is the focal length of the lens.
Substitute the value of v from equation (i) into equation (ii).
.
This expression is for the position of the object but distance is a positive value.
Therefore, the object distance is .
So, the correct answer is “Option B”.
Note: Note a real image formed by a real object is always inverted. Therefore, in this case the height of the image is negative and the height of the object is positive.
Since magnification is defined as the ratio of the height of the image to the height of the object, the value of magnification is negative.
When a real image is formed, the position of the image is positive and the position of the object is negative. Therefore, the ratio is negative. Again we prove that the magnification is negative.
Formula used: magnification
Complete step by step answer:
It is given that a convex lens produces a real image. The size of the image produced is said to m times larger than the size of the object.
We will use the formula for magnification. The magnification is the ratio of the height of the image to the height of the image. A real image is always inverted. Therefore, the value of magnification is negative. This means that magnification is (-m).
The value of magnification is equal to
The relation between the position of the object and its image is given as
Substitute the value of v from equation (i) into equation (ii).
This expression is for the position of the object but distance is a positive value.
Therefore, the object distance is
So, the correct answer is “Option B”.
Note: Note a real image formed by a real object is always inverted. Therefore, in this case the height of the image is negative and the height of the object is positive.
Since magnification is defined as the ratio of the height of the image to the height of the object, the value of magnification is negative.
When a real image is formed, the position of the image is positive and the position of the object is negative. Therefore, the ratio
Latest Vedantu courses for you
Grade 10 | CBSE | SCHOOL | English
Vedantu 10 CBSE Pro Course - (2025-26)
School Full course for CBSE students
₹37,300 per year
Recently Updated Pages
Master Class 12 Business Studies: Engaging Questions & Answers for Success

Master Class 12 Economics: Engaging Questions & Answers for Success

Master Class 12 Maths: Engaging Questions & Answers for Success

Master Class 12 Biology: Engaging Questions & Answers for Success

Master Class 12 Physics: Engaging Questions & Answers for Success

Master Class 12 English: Engaging Questions & Answers for Success

Trending doubts
a Tabulate the differences in the characteristics of class 12 chemistry CBSE

Why is the cell called the structural and functional class 12 biology CBSE

Which are the Top 10 Largest Countries of the World?

Differentiate between homogeneous and heterogeneous class 12 chemistry CBSE

Derive an expression for electric potential at point class 12 physics CBSE

Who discovered the cell and how class 12 biology CBSE
