Using the lens formula 1/f = 1/v - 1/u, we find v = 33.33 cm.

Using the lens formula 1/f = 1/v - 1/u, we find v = 10 cm.

A concave lens always forms a virtual and erect image regardless of the object position.

Concave lenses always produce virtual and upright images.

Concave lenses always produce virtual and upright images.

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

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

Using the lens formula 1/f = 1/v - 1/u, we have 1/f = 1/40 - 1/(-60) = 1/40 + 1/60 = 1/24. Therefore, f = 24 cm.

Power (P) = 1/f, so f = 1/P = 1/(-2) = -0.5 m = -50 cm.

A negative power indicates a concave lens.

Image distance (v) = Object distance (u) + Distance between object and image = 30 cm + 70 cm = 40 cm.

Power is inversely proportional to focal length. If f is doubled, P = 1/f will halve.

Magnification (m) = v/u = 1 when image distance equals object distance.

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.

When the object distance equals the focal length, the image is formed at infinity.

When the object is at the focal length, the image is formed at infinity.

Using the lens maker's formula, f = R/(n-1) = 20/(1.5-1) = 40 cm.

Using the lens maker's formula, f = R/(n-1) = 30/(1.5-1) = 30/0.5 = 60 cm.

Using the lens maker's formula, f = R/(n-1) = 30/(1.5-1) = 30/0.5 = 60 cm.

The eyepiece of a compound microscope is a convex lens.

The objective lens is the one closest to the object being viewed.

Using the lens maker's formula, f = (R1 * R2) / (n - 1) * (1/R1 - 1/R2), we find f = 12 cm.

The focal length of a lens decreases when immersed in a medium with a higher refractive index than air.

As the object moves closer, the image distance increases.

When the object is within the focal length of a convex lens, the image formed is virtual and upright.

Increasing the curvature of a lens decreases its focal length.

As the object distance increases, the size of the image formed by a convex lens increases until it reaches a maximum.

Using the lens formula 1/f = 1/v - 1/u, where v = 30 cm and u = -15 cm, we find f = 20 cm.

Using the lens formula, we find the focal length to be -12 cm.

Using the lens formula 1/f = 1/v - 1/u, we have 1/f = 1/(-15) - 1/(-10) = -1/15 + 1/10 = -1/30, thus f = -30 cm.