问题 问答题 简答题

简述显影的原理。

答案

参考答案:

感光片经拍摄感光,银盐发生光化学效应,记录了景物6<潜影。由于来自景物不同部位的光强度不同,感光片上不同部位羽受到的光的量不同,银盐发生的光化学效应的程度也不同。有些部位的银盐感光多,有些部位的银盐感光少,经过显影,使感光的卤化银还原成金属银粒,就形成不同密度的银粒构成的景物影像。

阅读理解

阅读理解。

    Each year, we celebrate many holidays here in America.

    On January 1, we welcome the coming of a new year like many people in other countries. And we

have another, four holidays on the first day of a month: April Fool's Day, May Day, Friendship Day

( Aug.1 ) and Grandparents Day ( Sept.1). The most important holiday for the youngpeople comes in

February. It is Valentine's Day. Lots of boys give red roses to girls as a present.

    People celebrate some holidays for their family members. We say thanks to our mothers in May and

celebrate Father's Day in the following month. In November many people return home for Thanksgiving

Day, so the whole family can stay together.

    There are also some interesting holidays for children.For example, Halloween comes at the end of

October. Children often play with pumpkin lanterns (南瓜灯) and put on all kinds of masks (面具).

    Of course, the most important festival is Christmas. After a year of work and study, people can enjoy

a long holiday, eat big meals, and visit family and friends.

1.How many holidays are there on the first day of a month in America? [ ]

A.Four.

B.Five.

C. Seven.

D.Ten.

2.What is the most important holiday for the young people in America? [ ]

A.Thanksgiving Day.

B.Christmas Day.

C.Valentine' s Day.

D.New Year's Day.

3.From the reading we know that Father's Day comes ______. [ ]

A.in May

B.in April

C.in June

D.in July

4.Halloween is one of the interesting holidays for ______. [ ]

A.children

B.mothers

C.girls

D.students

5.Many people return home in November because they want to ______.[ ]

A.enjoy a long holiday

B.visit their friends

C.eat big meals

D.spend Thanksgiving Day

单项选择题