7.4, 7.5 experiment optical instrutment

8/13/2019 7.4, 7.5 Experiment Optical Instrutment

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Aim : Investigate image

formed in pin-hole camera



1. Place a lighted candle in front of pin-hole camera

2. Adjust the position until a clear image

is seen3. Observe the characteristics of the

image formed



Situation haracteristics of imageformed

Image viewed in small pinholecamera

Camera moved toward flame/ Decrease the distance fromthe pinhole camera

Camera moved away from theflame

One enlarged pinholeConvex lens in front of thepin hole

Two pinhole

Five Pinhole



Discussion

1. What is the relationship between thedistance of the object and the size of theimage?

The longer the object distance, the smallerthe object. We can change the size of theimage by changing the object distance.



Discussion

2. Why does the convex lens make theimage on the screen sharper?

Convex lens converges the light onto thescreen.



Conclusion

• Image of the camera is affected by

• A) object distance

•

B) Size of the pin hole• C) The presence of the convex lens



Periscope

Observe the characteristics of theimage formed.

Upright, laterally inverted, virtual

Same characteristics of the imagesformed by the plane mirror.



• When taking the picture in the brightlight , a small aperture is used, to

avoid too much light enter the camera• shutter speed is increased

• When taking the picture in the dim/dark light , a big aperture is used.



Function of the camera parts

• Aperture- opening for light to enter the camera

• Diaphragm- control the size of the aperture

• Lens- Converge and focus the image on the film

•

Focusing ring- move the lens forward and backward• Shutter speed- control the length of time for film

to exposed to the light

• Film- capture the image of the object



• When taking the photograph of the far

object, the focusing rings used to movethe lens backward

• When taking the photograph of thenear object, the focusing rings used tomove the lens forward



Human eye



Function of the eye part

• Iris- control the size of the pupil

• Pupil – allow light to enter the eye

•

Eye lens - converge and focus the lightand form image on the retina

• Ciliary muscle- control the thickness ofthe lens



What happen to the eye in the

bright lighting condition?

• The size of the pupil become smaller.

• This is to avoid too much light fromentering the eye.

• The iris change the size of the pupil



How the eye focus the image ofthe near object on the retina

• Ciliary muscle change the shape of thelens

• The lens thicken



How the eye focus the image of

the distant object on theretina???

• Ciliary muscle change the shape/thickness of the lens

• The lens becomes thinner



similarities

7.4, 7.5 experiment optical instrutment

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