The Way Science Works
98-1 academic year, final examination, with answers
1. What are the two inventions that lead to the award of Nobel Prize in Physics in 2009 ?
Optical fiber and CCD (Charge coupled device).
2. Why diamond looks brighter than usual gem stone or glass even if cut to be the same shape ?
Diamond has the largest refractive index, so has strongest total reflection to come out from the flat side (opposite to the cone side), making diamond looks brightest.
3. What are the two major advantage of using number system ?
Accurately represent any large number in compact numerical symbols ; only single digit rule is rule is needed when performing arithmetic operations or calculations.
4. Explain what is a transistor, describe its structure and function.
Transistor is a device made from sandwich two (p- and n-) types of semiconductor. It has three electrodes, namely source, drain and gate. The voltage applied at gate controls the flow of electric current from source to drain. Transistor and be used as an amplifier in compact radio or a NOT gate in digital circuits (IC).
5. Draw diagram to show the way DRAM (dynamic random access memory) works (i.e. how it read and write bits from and to a certain address space).
Figure : http://163.13.111.54/science_works/080_Total_Recall.jpg (right page)
Write bits into DRAM :
(1) A DRAM chip has addesss and data lines/wires forming a cross network, each connect to the gate and the source of a transistors. Each transistor has a capacitors connect to it, as the figure shows.
(2) The address line/wire of the desired addess is charged. Since it is connected to an array of transisor gates, this opens up the channel from source to drain.
(3) Current are send to data lines depends of whether their bit is 1 or 0. Although data lines connects to all memory addresses, but only those with their address charged has open transistor allowing current to flow in to charge theose capacitor behind.
(4) the address lines switched off, no current can come out from capacitors, so the bit pattern is stored as charge in capacitors.
Read bits from DRAM :
(1) The address line which connect to the desired location of memory is chanrged, this results in the transistor gate changred, current can flow between source and drain. For those capacitors behind them (transistors) previously stored with charge, the current flow out of them. This current leads to data lines and can be detected as bit values 1 or 0.
6. What is the physics phenomenon help a radio to tune to a station one like to listen ?
Resonance.
7. Describe the procedure to make a music CD or movie DVD.
(1) Photoresit is coated on the surface of a glass disc, focused laser light beam is shained on and off onto the photoresist surface according to the master data on type or on disk. (2) The area not shined by light can be wahsed away by a special kind of solvent leaving the glass disc partly covered by exposed phtoresist. (3) The erosive gas is used to etch those unproteded region to form rough pit, after this entire glass disc has been treated this way, another kind of solvant is used to remove the reminng photoresist. (4) Platinum is deposited on glass surface, then the based glass disc is seperated from the metal to form a seal/chop. (5) The CD body is resin, it become soft when heated. Stamp the platinum seal on the warm soft CD and all the digial marks on the seal is pressed onto the CD. This "printing" process can be done very fast, about one piece per second. (6) The pressed side of the CD is coated plated with alunimum to make it reflecsive, and finally the information of CD is colour printed on top of the metal.
8. What are primary colours of light ?
Red, green and blue.
9. Does high ISO value of film or camera mean sensitive or less sensitive ?
Sensitive.
10. Write down the number seven in binary form.
111.
11. Mechanical calculating machines eventually do not been developed to become efficient computers, why ?
Gear wheels does not work well in a complicated inter-linked system. Such machine can be built but can not work reliably.
12. Which colour of light has shorter wave length ? red or blue ?
Blue.
13. What is photoresist ? How are micro/nano scale circuits made on silicon chip with the area of a finger nail ?
Photoresist are chemical substance that change solubility in specific solvent when shined or not shined by light. In photolithography
14. What is the simple while fundamental reason that made a pin-hole camera works.
Light beam travels along a straight line.
15. In "Visions" TV series professor Kaku mentioned three scientific revolution.
Quantum revolution, computer revolution and bio-molecular revolution.
16. Explain why a piece of semiconductor is needed in a digital (electronic) thermometer.
The conductivity within a piece of semiconductor is sensitive to temperature, so measure the magnitude of electric current passing through reflect how worm the surrounding is.
17. Write down all possibility of a half adder in the form of true false table, you should have input A, B, output O and carry-in C.
A B O C 0 0 0 0 0 1 1 0 1 0 1 0 1 1 0 1
18. Why many ancient currencies use a non-decimal system.
The number "10" can not be divided by daily used number 3 and 4, on the other hand, the number "12" can.
19. What is the topic you learn most from the course.
(You should recall the one you learn most and explain how you learn a lot form that topic.)
20. What is the topic you like most in the course.
(You should recall and write down the one you like most and explain why.)