Which term denotes the plane of focus perpendicular to the axis of the lens?

• A. Sensor
• B. Focal Plane
• C. Exposure
• D. Focus

Answer: (B)

The focal plane is the plane perpendicular to the lens’s optical axis where the image is formed. When light from a point in the scene passes through the lens, it is brought to a focus at this plane, and the sensor (or film) sits there to capture a sharp image. When you adjust focus, you’re aligning the subject’s distance so its light converges on that plane, making the image crisp. The other terms don’t describe this plane: the sensor is the recording surface, exposure is about the amount of light captured, and focus is the act or state of achieving sharpness, not the plane itself.