Understanding Lens Formula

What is the lens formula and how is it expressed mathematically?

• 1/f = 1/v + 1/u

• 1/f = 1/u - 1/v

• 1/f = 2/v + 1/u

• f = v + u

If a convex lens has a focal length of 10 cm, what is the image distance for an object placed 30 cm from the lens?

• 5 cm

• 15 cm

• 20 cm

• 7.5 cm

Explain the difference between real and virtual images in terms of lens behavior.

• Real images are always larger than virtual images.

• Real images are formed on the same side as the object.

• Real images can be projected and are formed on the opposite side of the lens; virtual images cannot be projected and are formed on the same side as the object.

• Virtual images can be projected onto a screen.

A concave lens has a focal length of -15 cm. Calculate the image distance for an object placed 10 cm from the lens.

• -30 cm

• 5 cm

• 15 cm

• 30 cm

How does the sign convention apply to the lens formula?

• The sign convention only applies to the focal length of the lens.

• The sign convention applies to the lens formula by defining positive and negative values for focal length, object distance, and image distance based on the type of lens and the position of the object and image.

• Object distance is always considered negative in all cases.

• The lens formula does not require any sign convention.

An object is placed 25 cm from a convex lens with a focal length of 5 cm. Determine the nature of the image formed.

• The image is real and inverted.

• The image is virtual and inverted.

• The image is real and upright.

• The image is virtual and upright.

What happens to the image distance when the object is moved closer to a convex lens?

• The image distance becomes negative.

• The image distance increases.

• The image distance remains the same.

• The image distance decreases.

Describe the characteristics of a real image formed by a convex lens.

• A real image formed by a convex lens is inverted, real, and can be projected onto a screen.

• A real image is upright and cannot be projected onto a screen.

• A real image is always smaller than the object and cannot be captured.

• A real image formed by a convex lens is virtual and magnified.

If the image distance is negative, what type of image is formed?

• Magnified image

• Virtual image

• Inverted image

• Real image

Calculate the image distance for an object at infinity using a concave lens with a focal length of -20 cm.

• -30 cm

• 0 cm

• -10 cm

• -20 cm