How safe are your sunglasses?

This task is about how light effects the eye and the use of sunglasses.
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Read the information that follows and use it to answer the questions. 

Question

a)  i)  Which diagram shows what the eye would look like in bright light?

    • Smallpupil.png

    • Bigpupil.png

Explain your answer.

Question

     ii)  Which diagram shows what would change if you were wearing sunglasses?  

    • Smallpupil.png

    • Bigpupil.png

Explain your answer.

Question 1Change answer

Here is some information about choosing sunglasses that are safe:
  • All sunglasses stop some sunlight from reaching the eyes.
  • Only some sunglasses also stop ultraviolet light (UV) from reaching the eyes.
   
b)  UV light can "sunburn" the retina causing temporary blindness. Scientists say it is dangerous to wear sunglasses that do not filter out UV light. Explain why scientists would say this about sunglasses, using:  
  • the information in the box, and
  • your own understanding of how the eye is protected from bright light.

Question

How can you tell which sunglasses are safe?

  • It is possible to test the amount of UV that can get through sunglasses.
  • There is a "safety standard" that sets the amount of UV it is safe to let in. This is either 99% or 100%. If they qualify, sunglasses have to display this safety sticker in Australia. It is not yet compulsory in New Zealand.
  • Cost is no guide to safety. Some cheap sunglasses are safe and some expensive ones are not.
 
c)  Who would be the best people to test and check sunglasses to see if they are safe?

    • the people who wear them

    • the people who sell them

    • technicians in testing laboratories

    • scientists who investigate eye safety

Explain your answer.

Question

d)  Who are the best people to set the safety standard for sunglasses? 

    • the people who wear them

    • the people who sell them

    • technicians in testing laboratories

    • scientists who investigate eye safety

Explain your answer.

Question 1Change answer

Some sunglasses are designed to be worn in places where people are at risk of getting too much UV over a long period of time. These glasses cut out much more light than ordinary sunglasses. If the retina gets too much UV for too long it can become damaged so badly that the person goes permanently blind. In Australia, they carry a safety sticker that looks like this.
e)  What do you think the safety sticker means?
     
 
f)  Why would glasses that cut out a lot of light need a sticker like this?