5.6P Explain the effects of different types of lens in producing real and…

The idea

A converging (convex) lens is thicker in the middle and brings parallel rays to a focus, so it can form a real image on the far side when the object is beyond the focal point; that image is inverted. When the object sits closer to the lens than F, the refracted rays diverge and only their backward extensions meet, giving a virtual, upright, magnified image — the magnifying-glass effect. A diverging (concave) lens is thinner in the middle and spreads parallel rays apart, so the rays never meet on the far side; the image is always virtual, upright and diminished, formed on the same side as the object. The key distinction is whether refracted rays actually converge (real) or only appear to diverge from a point (virtual).

What earns the marks

• States that a converging lens brings parallel rays to a focus and can form a real image on the opposite side of the lens.
• Explains that a real image from a converging lens is inverted and can be projected onto a screen.
• Explains that a converging lens forms a virtual, upright, magnified image when the object is closer than the focal length.
• States that a diverging lens spreads rays apart so they never converge to form a real image.
• Explains that a diverging lens always produces a virtual, upright, diminished image on the same side as the object.
• Distinguishes real from virtual by whether refracted rays actually meet or only appear to meet when extended backwards.

Common mistakes and how to put them right

• Claims a diverging lens can form a real image.

  Put it right: State that its image is always virtual, upright and diminished.

• Says a virtual image can be caught on a screen.

  Put it right: Explain that only a real image can be projected because the rays actually meet there.

• Assumes a converging lens always gives a real image.

  Put it right: Note that an object inside the focal length gives a virtual, magnified image.

• Describes the virtual image from a converging lens as inverted.

  Put it right: State that it is upright and magnified.

Exam tips

• Read the question for the object position before choosing real or virtual; the distance relative to F decides the outcome for a converging lens.
• Use the words 'actually meet' for real and 'appear to meet when extended' for virtual to make the distinction explicit.
• Check the lens shape in any diagram: thicker in the middle means converging, thinner in the middle means diverging.