Application of specular and diffuse reflection

There are several interesting applications of the distinction between specular and diffuse reflection. One application pertains to the relative difficulty of night driving on a wet asphalt roadway compared to a dry asphalt roadway. Most drivers are aware of the fact that driving at night on a wet roadway results in an annoying glare from oncoming headlights. The glare is the result of the specular reflection of the beam of light from an oncoming car. Normally a roadway would cause diffuse reflection due to its rough surface. But if the surface is wet, water can fill i

Fig. 6.7.

n the crevices and smooth out the surface (Fig. 6.7). Rays of light from the beam of an oncoming car hit this smooth surface, undergo specular reflection and remain concentrated in a beam. The driver perceives an annoying glare caused by this concentrated beam of reflected light.

A second application of the distinction between diffuse and specular reflection pertains to the field of photography. Many people have witnessed in person or have seen a photograph of a beautiful nature scene captured by a photographer who set up the shot with a calm body of water in the foreground. The water (if calm) provides for the specular reflection of light from the subject of the photograph. Light from the subject can reach the camera lens directly or it can take a longer path in which it reflects off the water before traveling to the lens. Since the light reflecting off the water undergoes specular reflection, the incident rays remain concentrated (instead of diffusing). The light is thus able to travel together to the lens of the camera and produce an image (an exact replica) of the subject which is strong enough to perceive in the photograph.

Speaking

Exercise 23. Work in small groups (3– 4). Discuss the questions below, present your ideas to the group and compare with other groups’ ideas.

1. Describe the difference between diffuse reflection and specular reflection.

2. Explain what causes light rays to undergo diffuse reflection.

3. If a bundle of parallel incident rays undergoing diffuse reflection follow the law of reflection, then why do they scatter in many different directions after reflecting off a surface?

4. Perhaps you have observed magazines which have glossy pages. The usual microscopically rough surface of paper has been filled in with a glossy substance to give the pages of the magazine a smooth surface. Do you suppose that it would be easier to read from rough pages or glossy pages? Explain your answer.

5. Laser beams are made of light. In science fiction movies, laser beams are often shown as bright lines shooting out of a laser gun on a spaceship. Why is this scientifically incorrect?

Exercise 24. Explain the following terms.

Reflection Normal line Angle of incidence

Diffuse reflection Incident ray Angle of reflection

Specular reflection Reflected ray Absorption

Grammar. Participle as Adjectives (Participle I and Participle II).

Exercise 25. Circle the correct form of the participles used as adjectives in the following sentences.

1. The (breaking/ broken) dishes lay on the floor.

2. The (trembling/ trembled) children were given a blanket for warmth.

3. Compassionate friends tried to console the (crying/ cried) victims of the accident.

4. The (interesting/ interested) tennis match caused a great deal of excitement.

5. When James noticed the (burning/ burnt) building, he notified the fire department immediately.

6. The (exciting/ excited) passengers jumped into the lifeboats when notified that the ship was sinking.

7. The (smiling/ smiled) ‘Mona Lisa’ is on display in the Louver in Paris.

8. The wind made such (frightening/ frightened) noises that the children ran to their parents’ room.

9. The (frightening/ frightened) hostages only wanted to be left alone.

10. We saw the (advancing/ advanced) army from across town.

11. Mrs. Harris’s (approving/approved) smile let us know that our speeches were well done.

12. Our representative presented the (approving/ approved) plan to the public.

13. The food of that new restaurant was (disgusted/ disgusting).

Exercise 26. Rewrite the sentences using a participle clause.

Look at the woman who is dressed in blue. = Look at the woman dressed in blue.

The boy who is sitting next to the lady is my cousin. = The boy sitting next to the lady is my cousin.

1. The boy who was injured in the accident is still in hospital.

2. Cars which are made in Germany are usually expensive.

3. I gave some sweets for the small girl who was crying in the park.

4. I know an Italian restaurant which serves excellent spaghetti.

5. The boy who is making so much noise is my son.

6. The grammar books which were printed last week will be sent to all school.

7. I’d like to stay in a room that overlooks the sea.

8. The purse which was stolen from the room was found by police.

9. Many people who live in large cities hate crowds.

10. The snow which is falling on highway will make traveling dangerous.

Exercise 27. Join these sentences using present participle or perfect participle form.

Examples:

• I looked out of window. I saw my friend. = Looking out of window, I saw my friend.

• I took a shower, and then I went to work. = Having taken a shower, I went to work.

• As the children had been warned not to stay out too long, they came home early. =Having been warned not to stay out too long, they came home early.

1. The man didn’t want to see this girl, so he quickly went in the small room. 2. Suzy tried to phone her boyfriend but she didn’t realize that the telephone was out of order. 3. He had worked all his life, so he decided to take a long holiday.4. She had finished all the house work, and then she sat on the sofa to watch TV. 5. He failed the exam because he hadn’t studied.6. Jane is busy in the kitchen. She is cooking some fish for visitors. 7. As she had been advised by her doctor to lose weight, she started to go on diet.8. As I have never met your secretary before, I’m surprised to see how beautiful she is.9. The lady opened the door quietly and she saw her maid stealing the jewellery in drawer. 10. He had driven all day, so he was glad to get home and rest.

Writing

Exercise 28. Translate the sentences into English using active vocabulary and paying attention to translation of Participle (words in italics).

1. На межі поділу двох середовищ частина світла відбивається, а частина – заломлюється. 2. Кутом падіння називається кут між падаючим променем та перпендикуляром до межі поділу, проведеним у точці падіння. 3. Кут відбивання – це кут між відбитим променем і тим самим перпендикуляром. 4. Закони відбивання світла можна сформулювати наступним чином: a) Падаючий промінь, відбитий промінь і перпендикуляр до межі поділу двох середовищ, проведений у точці падіння променя, лежать в одній площині. б) Кут відбитого променя дорівнює куту падаючого променя. 5. Знаючи закони відбивання світла, легко пояснити, як відбуваються дзеркальне і розсіяне відбивання світла. 6. Якщо паралельні промені, які падають на поверхню, залишаються паралельними і після відбивання, то таке відбивання називається дзеркальним, а сама поверхня – плоским дзеркалом. 7. Дзеркальну, тобто гладеньку, поверхню використовують тоді, коли світловий пучок потрібно повернути в певному напрямку. 8. Якщо паралельний пучок світла падає на шорстку поверхню, перпендикуляри в точки падіння не є паралельними, тому відбиті промені також не є паралельними; і світло поширюється в різні сторони. 9. Розсіяним є відбивання світла, що падає на сторінки книг, зошитів, від поверхні Землі, Місяця. 10. Тому текст ми можемо читати при будь-якому положенні очей відносно книги, а Місяць бачимо, пересуваючись по Землі.

Exercise 29. Summarize all the information given in unit 2 and write the summary under the title ‘Reflection. Specular and Diffuse reflection’.