DIGITAL

1. The binary number 100101 is equal to

• A. 37
• B. 25
• C. 41
• D. 21

2. The number 28 converted to binary is

• A. 00111
• B. 111
• C. 11100
• D. 10110

3. Which of these is NOT a digital storage device?

• A. DVD disc
• B. music cassette tape
• C. external hard drive
• D. music CD

4. A DVD disc is scanned using a laser of wavelegth 640 nm. The depth of the pits on the DVD should be

• A. 320 nm
• B. 1280 nm
• C. 160 nm
• D. 2560 nm

5. How many binary 1's and 0's does an 8 gigabyte memory stick contain?

• A. about 8 million
• B. about 8 billion
• C. about 64 million
• D. about 64 billion

6. Which one of these is not an advantage of digital storage of media?

• A. faster retrieval of data
• B. high quality of music / pictures / data
• C. no quantisation errors
• D. data can be processed and manipulated quickly

7. The capacitance of a component is defined as

• A. the potential difference per unit charge stored
• B. the charge per unit potential difference stored
• C. the energy per unit charge stored
• D. the charge per unit energy stored

8. A capacitor of capacitance C is charged to a voltage V, and a charge Q is stored. If a capacitor of capacitance 4C is connected to a supply of voltage 12V, the stored charge will be

• A. Q/48
• B. Q/3
• C. 3Q
• D. 48Q

9. CCD stands for

• A. capacitance conducting device
• B. charged capacitance discharge
• C. charge coupled device
• D. conducting capacitance discharge

10. A rectangular CCD measures 40mm x 20mm and contains pixels that measure 10 μm x 10 μm. How many pixels are there in total?

• A. 80k pixels
• B. 80M pixels
• C.800k pixels
• D. 8M pixels

11. Light is incident on a pixel on a CCD. The charge that accumulates on it is proportional to

• A. the number of photons incident on the pixel
• B. the frequency of the light
• C. the energy of each photon
• D. the votage applied to the CCD

12. If a CCD has a quantum efficiency of 0.4 , it means that

• A. 40% of all photons are not detected
• B. 40% of the photons cause an electron to be released from the silicon
• C. 40% of the electrons released are detected by the external circuit
• D. 40% of the electrons released remain as an accumulated charge on the pixel

13. Three distant stars appear close together in a line in the night's sky. They can just be resolved by a CCD if the light falls on a line of at least

• A. 3 pixels length
• B. 5 pixels length
• C. 6 pixels length
• D. 9 pixels length

14. A small rectangle measuring 1.5mm x 3mm is photographed using a digital camera. The image produced on the CCD measures 6mm x 12 mm. The magnification of the camera is therefore equal to

• A. 4
• B. 16
• C. 0.25
• D. 0.0625

• A. Instant retrieval of images
• B. higher quantum efficiency
• C. wider range of detectable wavelengths
• D. higher magnification possible