A tall man stands in front of a converging lens of focal length . What is the height of his image?

Suppose that an object is located in front of a thin convex lens whose radius of curvature is equal to . Will the image be oriented up or down? Will it be a real image, or a virtual one?

A ray of light passes through the focal point and then strikes a thin lens. After refraction, this ray:

Two small blue LEDs, both with a wavelength of are located away from you. You have a telescope with a diameter objective. How far apart are the LEDs in if you can barely resolve them as two objects?

How will the image of an object appear if it is located outside the focal length of a converging lens?