What is the focal length of a lens that forms a virtual image at a distance of 20 cm when the object is placed at 10 cm?
Practice Questions
1 question
Q1
What is the focal length of a lens that forms a virtual image at a distance of 20 cm when the object is placed at 10 cm?
5 cm
10 cm
15 cm
20 cm
Using the lens formula, 1/f = 1/v - 1/u. Here, v = -20 cm (virtual image), u = -10 cm. Solving gives f = 5 cm.
Questions & Step-by-step Solutions
1 item
Q
Q: What is the focal length of a lens that forms a virtual image at a distance of 20 cm when the object is placed at 10 cm?
Solution: Using the lens formula, 1/f = 1/v - 1/u. Here, v = -20 cm (virtual image), u = -10 cm. Solving gives f = 5 cm.
Steps: 8
Step 1: Understand the lens formula, which is 1/f = 1/v - 1/u.
Step 2: Identify the values for v and u. The virtual image distance (v) is -20 cm (negative because it's virtual) and the object distance (u) is -10 cm (negative because it's on the same side as the object).
Step 3: Substitute the values into the lens formula: 1/f = 1/(-20) - 1/(-10).
Step 4: Calculate 1/(-20) which is -0.05 and 1/(-10) which is -0.1.
