A convex lens has a focal length of 20 cm. If an object is placed at a distance
Practice Questions
Q1
A convex lens has a focal length of 20 cm. If an object is placed at a distance of 30 cm from the lens, what is the distance of the image from the lens?
60 cm
15 cm
30 cm
10 cm
Questions & Step-by-Step Solutions
A convex lens has a focal length of 20 cm. If an object is placed at a distance of 30 cm from the lens, what is the distance of the image from the lens?
Step 1: Identify the given values. The focal length (f) of the lens is 20 cm, and the object distance (u) is -30 cm (we use a negative sign for object distance in lens formula).
Step 2: Write down the lens formula: 1/f = 1/v - 1/u.
Step 3: Substitute the known values into the lens formula: 1/20 = 1/v - 1/(-30).
Step 4: Simplify the equation: 1/20 = 1/v + 1/30.
Step 5: Find a common denominator for the right side of the equation. The common denominator for 20 and 30 is 60.
Step 8: Invert the equation to find v: v = 60/2 = 30 cm.
Step 9: Since the image distance is positive, it means the image is formed on the opposite side of the lens.
Lens Formula – The lens formula relates the focal length (f), the object distance (u), and the image distance (v) in a lens system, expressed as 1/f = 1/v - 1/u.
Convex Lens Properties – A convex lens converges light rays and can produce real or virtual images depending on the position of the object relative to the focal point.
