A convex lens has a focal length of 20 cm. If an object is placed at a distance of 40 cm from the lens, what is the distance of the image from the lens?
Practice Questions
1 question
Q1
A convex lens has a focal length of 20 cm. If an object is placed at a distance of 40 cm from the lens, what is the distance of the image from the lens?
20 cm
40 cm
60 cm
80 cm
Using the lens formula 1/f = 1/v - 1/u, where f = 20 cm and u = -40 cm, we find v = 20 cm. The image is formed at 20 cm on the opposite side.
Questions & Step-by-step Solutions
1 item
Q
Q: A convex lens has a focal length of 20 cm. If an object is placed at a distance of 40 cm from the lens, what is the distance of the image from the lens?
Solution: Using the lens formula 1/f = 1/v - 1/u, where f = 20 cm and u = -40 cm, we find v = 20 cm. The image is formed at 20 cm on the opposite side.
Steps: 12
Step 1: Identify the given values. The focal length (f) of the lens is 20 cm, and the object distance (u) is 40 cm.
Step 2: Remember that in lens formulas, the object distance (u) is taken as negative. So, u = -40 cm.
Step 3: Write down the lens formula: 1/f = 1/v - 1/u.
Step 4: Substitute the known values into the lens formula: 1/20 = 1/v - 1/(-40).
Step 5: Simplify the equation: 1/20 = 1/v + 1/40.
Step 6: Find a common denominator for the right side. The common denominator for 20 and 40 is 40.
