CH15 LIGHT reflection refraction light energy.pptx

light chapter

1. WHAT MAKES THINGS VISIBLE

2. A tiny mirror M is fixed on a piece of cardboard placed on a table. The cardboard is illuminated by light from a bulb. The position of eye with respect to position of bulb is shown in the figure as A, B, C and D. In which position mirror will be visible?      

3. LET’S RECAP

4. MULTIPLE REFLECTIONS When two mirrors are kept inclined at an angle, they can together form multiple images. This is because the image formed by one mirror forms the object for the other mirror.

5. The periscope is a device for observation. It helps to observe a given object if the object can not be seen through direct sight with line of sight.  Kaleidoscope is also an optical device which is used for observing the repeated form of reflection of a given object.  

6. TRACK YOUR PROGRESS

7. LET’S RECAP

8. The ciliary body produces the fluid in the eye called aqueous humor. It also contains the ciliary muscle, which  changes the shape of the lens when your eyes focus on a near object . This process is called accommodation. The light coming from an object enters the eye through cornea. The main function of cornea is  to protect the eye but it also helps in focussing some light   By changing its shape, the lens changes the focal distance of the eye. In other words, it  focuses the light rays that pass through it (and onto the retina) in order to create clear images of objects that are positioned at various distances . It also works together with the cornea to refract, or bend, light.

9. The optic nerve emerges from the back of the eye ball. This nerve goes to the brain. Blind Spot: The junction of retina and the optic nerve is called the blind spot. There is no photosensitive cell at this spot, and hence  no image is formed at this spot on the retina .

10. Write down the names of parts of the eye in the blank spaces shown in the figure.        

11. Give one word answers:

12. Even after the object is removed, the impression of an object seen by the eye remains on the retina for 1/16th of a second . If we see another object before this time, the impressions of the two merge to give us a sense of continuity. This eye property is known as persistence of vision.

13. LET’S RECAP

14. Shibu is a fussy eater and he likes to eat only sweets and fried foods. He dislikes eating fruits and vegetables. In your evaluation, is this diet good for him? What should he eat to keep himself (especially his eyes) healthy?