An object is placed 4 cm in front of a concave lens of focal length 3 cm. Using the lens equation, find where the image will form and state whether it is a real or virtual image.

To find where the image will form, you can use the lens equation:

1/f = 1/v - 1/u,

where:
- f is the focal length of the lens,
- v is the distance of the image from the lens,
- u is the distance of the object from the lens.

In this case, the object is placed 4 cm in front of a concave lens of focal length 3 cm. Plug these values into the lens equation:

1/3 = 1/v - 1/4.

Now, let's solve for v:

1/v = 1/3 + 1/4,
1/v = (4 + 3) / (3*4),
1/v = 7/12.

To isolate v, take the reciprocal of both sides:

v = 12/7.

Therefore, the image will form 12/7 cm away from the lens.

To determine whether the image is real or virtual, we need to examine its position relative to the lens. If the image distance (v) is positive, it means the image is formed on the opposite side of the object (on the same side as the observer) and hence is a real image. In this case, the image distance (v) is positive (12/7 cm > 0 cm), so the image is real.