If a concave lens has a focal length of -20 cm, what is the nature of the image

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Question: If a concave lens has a focal length of -20 cm, what is the nature of the image formed when an object is placed at 30 cm from the lens?

Options:

Correct Answer: Virtual and upright

Solution:

For a concave lens, the image formed is virtual and upright when the object is placed beyond the focal length.

If a concave lens has a focal length of -20 cm, what is the nature of the image formed when an object is placed at 30 cm from the lens?

If a concave lens has a focal length of -20 cm, what is the nature of the image formed when an object is placed at 30 cm from the lens?

Step 1: Identify the type of lens. The lens is a concave lens.
Step 2: Note the focal length of the lens. The focal length is -20 cm (negative for concave lenses).
Step 3: Determine the position of the object. The object is placed at 30 cm from the lens.
Step 4: Compare the object distance (30 cm) with the focal length (-20 cm). Since 30 cm is greater than -20 cm, the object is beyond the focal length.
Step 5: Understand the properties of a concave lens. A concave lens always forms a virtual image when the object is placed beyond the focal length.
Step 6: Conclude that the image formed is virtual and upright.

Lens Formula – Understanding the relationship between object distance, image distance, and focal length using the lens formula (1/f = 1/v - 1/u).
Image Characteristics – Identifying the nature of the image (real/virtual, upright/inverted) formed by concave lenses based on object placement relative to the focal length.