F2 IS 2nd Term WS13 Answers

2nd Term WS 13 Submission date：_____________ Name：______________________ Class & no.：2 _________(     )

11.3    Limitations of our eyes

11.4    Eye defects     

i      Words to know:

	English term	Write the words again	Chinese term
1	Limitation		限制
2	Telescope		望遠鏡
3	Microscope		顥微鏡
4	Blind spot		盲點
5	Eye defects		眼睛毛病
6	Short / Long sight		近 / 遠視
7	Near / Distant		近 / 遠
8	Concave / Convex lens		凹 / 凸透鏡
9	Cataracts		白內障
10	Artificial lens		人工晶體
11	Colour-blindness		色盲
11	Hereditary disease		遺傳病

i    Fill in the blanks:

1          Our eyes have limitations. We cannot see object clearly when they are too close / large

         or too large / close or too small.

2          We can use suitable instruments to extend our vision. For example, we can use ______________________

l   microscope to observe objects that are too small like bacteria;

l   telescope to observe objects that are too far away such as stars.

3           The light from the object focused on the blind spot produces no sense of sight because

there are no light receptors on this area.

4          Besides limitations of our eyes, if we have an eye defect, we cannot see things clearly. The followings are some examples:

l   short sight

l   Long sight

l  cataract

l   Colour-blindness

5           Two common eye defects are short sight and long sight which can be corrected by wearing spectacles with suitable lenses.

6           The lens of an eye is normally clear / colourless / transparent. If the lens becomes cloudy, vision becomes unclear.

This eye defect is called a cataract. It can be treated by replacing the cloudy lens with an

artificial lens.

7           Colour-blindness is a kind of eye defect that the patients cannot distinguish certain colours.

The most common one is red-green colour-blindness – the patient cannot distinguish between red and green.

It is caused by defects in or the absence of certain cones on the retina.

It is a hereditary disease and cannot be cured.