物理透鏡 DSE、CE 選擇題（第 5 頁）

41.

If points $F$ and $F'$ represent the focal points of a concave lens, which of the following ray diagrams correctly shows the path of a light ray through the lens ?

Four ray diagrams A to D for a concave lens

42.

Object O and its upright image I on the same side, with points A, B, C and D on the axis

In the above figure, the image $I$ of an object placed at $O$ is produced by a single lens. If the magnification is $2$ , what kind of lens has been used and where must it have been placed ?

43.

Narrow parallel beam entering a box containing two lenses X and Y and leaving as a wider parallel beam

As shown in the diagram, a narrow parallel beam of light is converted to a wider parallel beam by placing two lenses $X$ and $Y$ in the positions shown. Which of the combinations below when correctly chosen and installed could produce the effect required ?

	Lens $X$	Lens $Y$
(1)	convex	concave
(2)	concave	concave
(3)	concave	convex

44.

Which of the following will produce a diminished image of an object $O$ ? ( $f$ is the focal length)

Four diagrams A to D of an object O at different distances in front of a convex lens, with distances f and f marked

45.

Lamp, lens and screen with the sharp image formed at P in front of the screen

A lens gives a sharp image of the lamp at $P$ as shown in the figure above. Which of the following methods could give a sharp image of the filament on the screen ?

(1)Move the screen towards the lens.

(2)Move the lamp closer to the lens.

(3)Replacing the lens by another lens of longer focal length.

46.

Which of the following statements concerning the properties of virtual images formed by a lens is/are correct ?

(1)Virtual images can be seen by the naked eye.

(2)Virtual images can be formed on a screen.

(3)Virtual images can be photographed with a camera.

47.

An object is placed $20$ cm in front of a converging lens of focal length $30$ cm. Which of the following statements about its image is/are correct ?

(1)The image is real.

(2)The image is magnified.

(3)The image is erect.

48.

Ray of light incident on a concave lens; F is the focus on each side

A ray of light is incident at a concave lens. $F$ is the focus of the lens. Which of the following diagrams correctly shows the path of the emergent ray ?

49.

Points P, Q, R, S, lens position L, focus F and a real image I on the principal axis

A real image of an object is formed at $I$ by a lens placed at $L$ . If the focus of the lens is at $F$ , the object must have been placed near to

50.

Lamp, convex lens L and screen with a sharp image formed on the screen

A convex lens $L$ is placed between a screen and a lamp. A sharp image is formed on the screen as shown in the above figure. Which of the following statements concerning the image are correct ?

(1)The image is larger than the object.

(2)The image is real.

(3)The image is inverted.