The Refractive Index Of Water PDF

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Summary

Experiment for the refractive index of water...

Description

Name zID

PHYS1110 – Everyday Physics – Experimental report Author of this report Collaborator (if applicable) Celine Wong Name Z5308335 zID

Investigation title: The Refractive Index Of Water Photographic evidence of investigation and experimental set up Author with set up (and collaborator, if Author’s student card applicable)

Aim of the investigation To observe the refraction of light and using Snell’s law for calculations Risk Controls Hazards (Step 3)

Associate d risks (Step 4) -

Filling container

Spillage of water

Slip and fall, injuring yourself or others

Poking yourself or others

Injury from being poked

-

Using a skewer

Tasks

Existing controls

-

I, Celine Wong, agree to follow the risk controls Results hwater (cm) Uncertainty in hwater (cm) 3 0.05 6 0.05 9 0.05 12 0.05 15 0.05

Analysis

Clean up any spills as soon as possible Carefully pour water into the container (using a jug may help) Avoid pointing the pointy end of the skewer towards yourself and others

hcoin (cm) 2 3.4 4.9 5.5 8.7

Risk rating with existing controls (Step 5) C L R 2

C

M

2

E

L

Uncertainty in hcoin (cm) 0.05 0.05 0.05 0.05 0.05

hwater vs hcoin 18.0 16.0

14.0

hwater (cm)

12.0 10.0

8.0 6.0 4.0

2.0 0.0 0.0

2.0

4.0

6.0

8.0

10.0

12.0

hcoin (cm)

Equation of line of best fit: Since nwater = gradient

y =1.85 x +5.07 ×10−2 ∴ nwater = 1.85

The uncertainty is calculated by halving the difference between the minimum and maximum gradient. Equation of max gradient line: Equation of min gradient line:

y =1.82 x −0.741 y =1.76 x −0.426

1.82 −1.76 =0.03 2 nwater = 1.85 ± 0.03

Uncertainty in nwater = ∴

Part 2

As the incident angle increases, the straw submerged in the water is observed to not be aligned with the straw that is out of the water. As a result, light is refracted which increases as the angle increases.

Answers to experiment questions c nmedium= vacuum 1. c medium n1 sin θ2 = n2 sin θ1

Snell’s Law:

na sin w = nw sin a



nw =na × Since na = 1



nw =

sinw sina

sin w sin a

From the diagram

tan a=

∴

x hcoin

tan a tan w

Since

∴

sina sinw

=

and

x hwater

h coin h water

tan a=sin a =

tan w =

hcoin hwater

and

tan w =sinw



nw =

sin w sin a

=

h water rise =gradient = hcoin run

2. The expected value for nwater does not fit within the measured range of 1.85 ± 0.03 (1.83, 1.88). However, the measured value is not substantially different to the accepted value. This discrepancy could be the result of human error as it is difficult to accurately measure hwater whilst holding the coin stationary in the air and a ruler and reading the measurement. 3. The air cell method is a better technique to measure nwater, as it eliminates the struggle of measuring hcoin. As a result, an apparatus consisting of two glass plates and an air gap is submerged into a container of water. A monochromatic light source is directed through two slits on opposite sides of the container. The air cell is then rotated until no light is passed through. The light source is rotated again until the light cannot be observed on the other end again. The angle of rotation between the first and second obstruction of light is recorded. The following equations are then used to calculate nwater:

nwater sinA= ng sinr =na sin 90=na Refractive index of water (nwater) =

na a = sinA sinA

Diagram of Air Cell Apparatus

since na = 1

(schoolphysics n.a.)

4. Light travels at different speeds when entering a different medium due to the different densities. As a result, when light

travels in water in comparison to air, it slows down and bends towards the normal. Therefore, we observe an image of the object to be bent. This phenomenon can be written as Snell’s law. Snell’s Law:

n1 sin θ2 = n2 sin θ1

Conclusion Overall, the refractive index of water was calculated to be 1.85 ± 0.03 although the theoretical value is 1.33. The second experiment resulted in an observation of the refraction of light due to the density of different mediums. Reference Gibbs, K. n.a., schoolphysics, viewed 11 April 2021, ....