There are strain components for the general state of strain

PROTECTING EYES FROM COMPUTER SCREENS

Many of us spend the bulk of the day looking at computer screens. Reading this article means there’s a good chance you’re looking at one right now.

But does looking at computer screens damage your eyes？ Professor Nathan Efron does not consider computer screens “harmful” to our eyes.

But he admits if you use one a lot, you increase your risk of becoming slightly more short-sighted –where your eyes focus well only on close objects while more distant objects appear blurred. This is especially the case for children and young adults, whose eyes are still developing.

In the shorter term, prolonged viewing of a computer screen can make any slight existing vision defects more noticeable. It can also give you what is sometimes known as “computer vision syndrome” – eye strain, headaches, gritty eyes and blurry vision. But this is only temporary and can be minimized by:

Adjusting the screen display so the contrast is high and the brightness feels comfortable.

Having lighting that does not produce glare on the screen.

Giving your eyes regular rests from looking at the screen (The Optometrists Association of Australia recommends you do this for five to ten minutes every one to two hours of computer use. It's a good time to make phone calls or do other tasks.)

1. Many of us spend much time looking at computer screens. {T; F}

2. Looking at computer screens for long time doesn’t damage children and young adults’ eyesight. {T; F}

3. Computer vision syndrome cannot be weakened. {T; F}

4. It’s good taking breaks during screen watching. {T; F}

5. Proper lighting is important to protect our eyes. {T; F}

A、As the relative elongation increases, the true strain and the engineering strain are the same

B、As the relative elongation decreases, the true strain will become significantly less than the engineering strain

C、For a small elongation the engineering strain is very close to the true strain

D、none the above

A.balance

B.strain

C.transfer

D.pension

细胞株(cell strain)