If the image distance of a convex lens is 40 cm and the object distance is 30 cm, what is the focal length of the lens?
Practice Questions
1 question
Q1
If the image distance of a convex lens is 40 cm and the object distance is 30 cm, what is the focal length of the lens?
10 cm
20 cm
30 cm
15 cm
Using the lens formula 1/f = 1/v - 1/u, we have 1/f = 1/40 - 1/(-30) = 1/40 + 1/30. Solving gives f = 20 cm.
Questions & Step-by-step Solutions
1 item
Q
Q: If the image distance of a convex lens is 40 cm and the object distance is 30 cm, what is the focal length of the lens?
Solution: Using the lens formula 1/f = 1/v - 1/u, we have 1/f = 1/40 - 1/(-30) = 1/40 + 1/30. Solving gives f = 20 cm.
Steps: 10
Step 1: Identify the given values. The image distance (v) is 40 cm and the object distance (u) is -30 cm (we use a negative sign for the object distance in lens formulas).
Step 2: Write down the lens formula: 1/f = 1/v - 1/u.
Step 3: Substitute the values into the formula: 1/f = 1/40 - 1/(-30).
Step 4: Simplify the equation: 1/f = 1/40 + 1/30.
Step 5: Find a common denominator to add the fractions. The common denominator for 40 and 30 is 120.
Step 6: Convert the fractions: 1/40 = 3/120 and 1/30 = 4/120.
