1.A 2.0 cm tall object is placed 15.0 cm in front of a convex lens. The focal le

Question

1.A 2.0 cm tall object is placed 15.0 cm in front of a convex lens. The focal length of the lens is 5.0 cm.

a) Calculate the image distance and image size (2pt).

b)Use the area below to construct a ray-diagram to locate the image. Be sure to indicate your scale, the image and its location (2pts)!

2. A 2.0 cm tall object is placed 15.0 cm in front of a concave lens. The focal length of the lens is 5.0 cm.

a) Calculate the image distance and image size (2pt).

b)Use the area below to construct a ray-diagram to locate the image. Be sure to indicate your scale, the image and its location (2pts)!

Explanation / Answer

1)
object distance, u = 15 cm

focal length, f = +5 cm (for convex lense f is always negative)

let v is the image distance

now, Apply 1/u + 1/v = 1/f

1/v = 1/f - 1/u

1/v = 1/(5) - 1/15

v = 7.5 cm <<<<<-------Answer

magnification,m = -v/u

= -(7.5)/15

= -0.5

image distance = m*object distance

= -0.5*2

= -1 cm <<<<<-------Answer

Here Image is real,invered and demagnified.

2)
object distance, u = 15 cm

focal length, f = -5 cm (for concave lense f is always negative)

let v is the image distance

now, Apply 1/u + 1/v = 1/f

1/v = 1/f - 1/u

1/v = 1/(-5) - 1/15

v = -3.75 cm <<<<<-------Answer

magnification,m = -v/u

= -(-3.75)/15

= 0.25

image distance = m*object distance

= 0.25*2

= 0.5 cm <<<<<-------Answer

Here Image is virtual,upright and demagnified.

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