物理 1995 年 DSE、CE 選擇題（第 4 頁）

31.

CRO display of a sine wave over two cycles; grid squares of 1 cm

The diagram shows the display on a CRO with the time base at $10\ \mathrm{ms\,cm^{-1}}$ and $Y$ -gain at $0.5\ \mathrm{V\,cm^{-1}}$ . Find the peak voltage and frequency of the signal applied across the $Y$ -plates.

	Peak voltage / V	Frequency / Hz
	$1$	$16.7$
	$1$	$25$
	$1$	$50$
	$2$	$25$

32.

Which of the following statements about X-rays is/are correct ?

(1)X-rays consist of fast moving electrons.

(2)X-rays can blacken photographic films.

(3)X-rays can be used to detect weapons hidden in luggage.

33.

A radioactive nuclide $W$ decays to a nuclide $Z$ by emitting one $\alpha$ -particle and two $\beta$ -particles as shown below.

$W\xrightarrow{\beta}X\xrightarrow{\alpha}Y\xrightarrow{\beta}Z$

Which of the following statements about nuclides $W$ , $X$ , $Y$ and $Z$ is/are correct ?

(1)

W

and

Z

are isotopes.

(2)

X

has the greatest atomic number.

(3)

Y

has the greatest mass number.