a light passes through a small pinhole, and incident on a screen.
What will be observed on the screen?
A: A
sharp bright point of the width equal to width the pinhole
B: A
bright point of the width equal to width the pinhole but of less
intensity
C: A
bright ring at the center surrounded by alternate dark and bright
rings
D: A
diffused bright point
举一反三
- ( )system<br/>interact with environment strongly. A: Open B: Close C: Bright D: Dark
- Seeing him, she<br/>seemed to ______ a little. (bright)
- In any case, the (()impressions<br/>of childhood and…liein<br/>the<br/>memory. A: bright B: transparent C: clean D: clear
- Work hard, ____ you will<br/>have a bright future. A: and B: or C: since
- 设置水平线居中，宽度为50%，颜色是红色的网页编码是（ ）。 A: <;br align="center" width="50%" color="red"/>; B: <;hr align="center" width="50%" color="red"/>; C: <;hr align="center" width="50%" color="red">;<;/hr>; D: <;br align="center" width="50%" color="red">;<;/br>;
内容
- 0
下面哪个是引用类样式( )[br][/br]{ A: B: p1 {font-size: 12px;color:red;}<br> C: div1 {width: 500px; height : 200px; boder:1px;}<br>p id="p1”><br>}<br>{ D: E: p1 {font-size: 12px;color :red;}<br>div1 {width: 500px ; height :200px ; boder: 1px;}<br>}<br>{ F: G: p1 {font-size : 12px ;color :red;}<br> H: div1 {width: 500px;height : 200px; boder: 1px;}<br>}<br>{ I: p1 {font-size: 12px;color :red;}<br>. div1 {width: 500px ;height :200px ; boder:1px;}<br>}
- 1
29. According to the professor, why were the<br/>jellyfish that the student saw glowing? A: They were communicating with each other. B: They were trying to confuse predators with<br/>bright flashes of light. C: They were avoiding predators by blending in<br/>with their surrounding. D: They were trying to light up the dark water<br/>so they could see prey.
- 2
有一个 div，它的 CSS 属性如下，请问它占多少空间_______ [br][/br] #div { width: 50px; heigth: 30px; padding: 3px; border: 1px dashed red; margin: 5px;[br][/br] } A: width: 50, height: 30 B: width: 68, height: 48 C: width: 58, height: 38 D: width: 59, height: 39
- 3
What<br/>is the relationship between the space charge width and doping<br/>concentration.() A: No<br/>relationship B: Proportional C: Inverse proportion D: Exponential
- 4
执行如下语句[br][/br]class point {[br][/br]private:[br][/br] int x_, y_;[br][/br]public:[br][/br] point( ) : x_(0), y_(0) { }[br][/br] point(int x, int y = 0) : x_(x), y_(y) { }[br][/br]};[br][/br]point a(2), b[3], *c[4];[br][/br]则point类的构造函数被调用的次数是______。 A: 2次 B: 3次 C: 4次 D: 5次