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##### :) Mathistillfun

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Physics
How do I do Question 2d), 4a) and 5a&b)?
Thanks a lot
Hope you can help ASAP
I wont copy word I just want to make sure I understand

Date Posted: 5 months ago
Views: 62
Snell
5 months ago
cannot read the top qns clearly

the diagram in the top left is incorrect.

hint for 2(d):
in which situation there would be no refraction of light for the archer fish?
:) Mathistillfun
5 months ago
Oh I am so sorry!! I will resend the pictures in the answers section
:) Mathistillfun
5 months ago
The diagram is incorrect is it because there should be a weak reflected ray internally before the emergent ray?
:) Mathistillfun
5 months ago
There will be no refraction when the incident ray is not deviated in other words the angle of incidence is zero at the water air boundary
OR
Simply when the fish is out of the water. No second medium for light to cross
:) Mathistillfun
5 months ago
Or I was thinking the fish would splash water in all directions randomly but thats dumb
:) Mathistillfun
5 months ago
Snell can you help me out with Question 5a & b and question 4a
Thanks a lot!!
Snell
5 months ago
Promise Chye said:
There will be no refraction when the incident ray is not deviated in other words the angle of incidence is zero at the water air boundary

this is one is close, but not complete

again,
in which situation there would be no refraction of light for the archer fish?
:) Mathistillfun
5 months ago
I still dont get it. If the fish jumps out of the water it will scare the prey away....
:) Mathistillfun
5 months ago
But if its right below the insect it could easily just catch it but the fish is not that smart tho
:) Mathistillfun
5 months ago
I think I kind of do understand what you are getting at but I don't see the reach of it

### See 3 Answers

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##### :) Mathistillfun's answer
1st
I would be grateful if u could help me out with this
Date Posted: 5 months ago
Snell
5 months ago
for (a),
the 2 conditions for TIR are met,
hence TIR can occur (& light would keep bouncing within the optical fiber of refractive index = 1.48)

for (b),
it is the working backwards for qn 4(d)

1. u got θ as angle of incidence for top side

2. calculate to obtain the angle of refraction for the left side (or end side)

3. use the refractive index formula and work out the angle of incidence
u may need to use trigo identities from AMath
:) Mathistillfun
5 months ago
Thanks a lot!!
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##### :) Mathistillfun's answer
I understand that the drawing is wrong however can someone help me out with q4a
Date Posted: 5 months ago
Snell
5 months ago
Promise Chye said:
The diagram is incorrect is it because there should be a weak reflected ray internally before the emergent ray?

nope

hints:
1. what is the critical angle value for the glass block?

2. what is the angle of incidence at side KL?

3. what phenomenon would occur at side KL?
:) Mathistillfun
5 months ago
Total internal Reflection
:) Mathistillfun
5 months ago
Thanks a lot!!
:) Mathistillfun
5 months ago
No wonder they said hence or otherwise draw the arrows representing light rays
:) Mathistillfun
5 months ago
The previous question calculating the critical angle
:) Mathistillfun
5 months ago
However I need help for the open ended question 4a) please thank you
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##### :) Mathistillfun's answer
I need help with question d
Date Posted: 5 months ago
Snell
5 months ago
Promise Chye said:
There will be no refraction when the incident ray is not deviated in other words the angle of incidence is zero at the water air boundary

this is one is close, but not complete

where shld the fish be for the above to be true?

no need for fish to jump out of water.

u still cannot figure it out, click this link:
https://www.physicsclassroom.com/class/refrn/Lesson-1/If-I-Were-an-Archer-Fish

bottom of page
Snell
5 months ago
Promise Chye said:
But if its right below the insect it could easily just catch it but the fish is not that smart tho

bingo! u got it!

btw, the qn does not ask u if the fish is that smart or not

anyway, in reality, the hit rate for archer fish is almost 100%, even for an angle of deviation of up to 40 deg.
:) Mathistillfun
5 months ago
Thanks a lot!