Words and word combinations to be remembered

incandescence – накал	derived – производный	increase – увеличиться
emission – выделение, распространение	lux – люкс	shine – светить, освещать
luminescence – свечение, люминесценция	inversely – обратно пропорционально	fluorescence – свечение, флуоресценция
a point source – точечный источник	electric bulb – электрическая лампочка	phosphorescence – свечение, фосфоресценция
illuminance – освещённость	under these conditions – при этих условиях	area – площадь, участок

Ex. 1. Translate from Russian into English:

Источник света, сила света, накаливание, флуоресценция, международная свеча (единица силы света), люкс (единица освещенности), люминесцентный, обратно пропорциональный, излучать, увеличивать, сравнивать, получать, зависеть от.

Ex. 2. Fill in the blanks:

1. Every source of light is known to have … .

2. Every object which emits light has a measurable … .

3. … the emission of light from a body from any cause other than high temperature.

4. … is the emission of light caused by high temperatures.

5. … is the amount of light falling on unit area of the surface per second.

6. Some substances emit light without becoming incandescent; we consider them to be … .

7. The light emitted by … is an example of luminescence.

8. A candle flame is an example of … .

9. Illuminance is inversely proportional to … .

10. Light from fluorescent sources … .

11. A source of light which is small compared to the area it illuminates is called … .

12. The derived unit of illumination in SI system of units is … .

13. We see luminous objects by the light they ... to the eye.

14. Every source of light has a luminous ... which is ... .

15. We see unlit electric bulb because it ... light which some other source of light ...

16. We see the Moon at night because it ... light which the Sun … .

Ex. 3. Choose the right word:

1. We use the standard candle to measure the luminous intensity of (some / any) luminous objects. 2. A source of light which is (large / small) compared to the area it illuminates is called a point source. 3. Illuminance of a surface is (directly / inversely) proportional to the luminous intensity of the source and (directly / inversely) proportional to the square of the distance from the source. 4. The candle is a unit used to measure (luminous intensity / illuminance). 5. The lux is a unit used to measure (luminous intensity / illuminance) in SI units. 6. All luminous objects emit (the same amount / different amounts) of light. 7. A source which has a luminous intensity of 25 candles is 25 times (more / less) intense than the standard candle. 8. We define the standard candle in terms of the light emitted by 1 cm² of a(n) (luminescent / incandescent / fluorescent) platinum metal surface maintained at a (random / fixed) temperature.

Ex. 4. Answer the following questions:

1. What kinds of light sources do you know? 2. What is a luminous intensity? 3. What is incandescence? 4. What is luminescence? 5. Could you give any examples of incandescence? 6. Could you give any examples of luminescence? 7. Is light from fluorescent sources incandescent? 8. What is a unit of the luminous intensity? 9. What is called a point source? 10. What does illuminance depend on?

Ex. 5. Say a few words about:

• luminous intensity

• incandescence

• luminescence

• a point source

• illuminance