snc2d – refraction index lesson plan - weebly...snc2d snc2d lesson plan refraction index (with...

$: SNC2D – Refraction Index Lesson Plan - Weebly...SNC2D SNC2D Lesson Plan Refraction Index (with Laboratory) 2 E3 demonstrate an understanding of various characteristics and properties$
SNC2D

SNC2D Lesson Plan Refraction Index (with Laboratory) 1

Lesson: Refraction Index (with Laboratory)

Course: Science, Grade 10 Academic (SNC2D)

Unit: Physics: Light and Geometric Optics

Duration: 75 minutes

Introduction

This lesson derives an understanding of the index of refraction (n) as it relates to the change in speed of light as it travels from one medium into another. The index of refraction is expressed as follows:

! = !!medium

! = !"#∠!!"#∠!

The laboratory component of the lesson assists students in discovering how to measure and calculate the specific value of the refraction index of a given medium.

Learning Expectations

Students will identify the bending/change in direction of light as a result of it changing speed in travelling form one medium into another.

Students will identify a correlation between the difference of the incident angle and refracted angle with that of the change in the speed of light.

Students will discover that the index of refraction can be determined by both: 1) the ratio of the speed of light in a vacuum to that the speed of light in a medium; and 2) the ration of the sine of the incident angle to that of the sine of the angle of refraction.

Students will recognize that, because light travels at different speeds in different mediums, each medium has a unique value for the index of refraction.

Students will be able to identify a medium from measuring and calculating a value for refraction index.

Students will derive an understanding of the refraction index from measurements and subsequent calculations made during the laboratory component of the lesson.

Curriculum Objectives

Overall Expectations Specific Expectations E2 investigate, through inquiry, the

properties of light, and predict its behaviour, particularly with respect to … refraction …

E2.1 use appropriate terminology related to light and optics…

E2.4 use an inquiry process to investigate the refraction of light as it passes through media of different refractive indices, compile data on their findings, and analyse the data to determine if there is a trend.

E2.6 calculate, using the indices of refraction, the velocity of light as it passes through a variety of media, and explain the angles of refraction with reference to the variations in velocity.

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E3 demonstrate an understanding of various characteristics and properties of light, particularly with respect to … refraction in lenses.

E3.4 explain the conditions required for partial reflection/refraction and for total internal reflection in lenses, and describe the reflection/refraction using labelled ray diagrams

E3.7 identify the factors, in qualitative and quantitative terms, that affect the refraction of light as it passes from one medium to another

From the Ontario Curriculum, Grades 9 and 10 Science (2008).

Prior Knowledge

This lesson is dependent upon prior knowledge cumulated over the unit. Students are expected to know how to draw and label a ray diagram and have some familiarity of refraction from previous lessons.

Although there are few, if any, concerns over potential hazards, students should have knowledge of proper laboratory safety procedures.

Materials/Resources

• Computer connected to a classroom projector with Microsoft PowerPoint (2010 for Windows, 2011 for Mac, or above)

• Ray boxes (one for every 4–5 students)

• Solid, transparent acrylic blocks (one block per ray box) with an index of refraction value of 1.52.

• ELMO and connected to a classroom projector

• Textbook – Science Perspectives 10. Nelson Education (2010).

• Laboratory worksheets

• Slides (PowerPoint file)

• Pencils, erasers, sharpeners, and rulers (students expected to bring)

Timeline of Lesson

Preparations

Before class, tests and sets up ray boxes in the laboratory area of the classroom.

25 min Lecture

Using PowerPoint slides, provide introductory lecture on the refraction of light.

10 min Demonstrate Laboratory

Teacher provides a demonstration, using the ELMO, a ray box, acrylic block, and laboratory worksheet, on how to conduct the laboratory.

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20 min Conducting the Laboratory

Students assigned into groups of 4–5 to conduct laboratory. Students then proceed to conduct the laboratory, using the ray boxes in the laboratory area of the classroom, to get results for the worksheet. When finished, students complete calculations and derive results/conclusions.

20 min Debriefing/Conclusions

Continuing with PowerPoint slides, teacher facilitates a whole-class discussion that further builds on the laboratory component to better drive an understanding of the index of refraction.

If time permitting, take up final questions on the last page of the worksheet.

Assessment Strategies

Success Criteria:

• Students, in groups of 4–5, will be able to conduct the required laboratory component of the lesson, producing accurate results required by the accompanying worksheet.

• Students will be able to use the results from the laboratory component to derive a specific conclusion as to the ratio of the sine of the incident angle to that of the sine of the angle of refraction.

• Students will be able to use an understanding of how the refraction index is determined and apply this to solving specific questions included in the worksheet.

Descriptive feedback is provided as part of both diagnostic and formative assessment throughout the entire lesson. During the laboratory component, the teacher has an opportunity to differentiate instruction further while verifying the accuracy of measuring results of each group. And as students attempt to derive the refraction index of the medium, both peer assessment and teacher feedback can help students derive the necessary results. In debriefing and deriving an understanding through conclusions, students are provided an opportunity to ask further questions as well as attempt to apply acquired knowledge to solve questions at the end of the worksheet. The teacher can use the worksheet as a summative assessment of each student.

Refraction+of+Light+Laboratory+–+Measuring+the+Speed+of+Light!

!

Name!!

SNC2D:!Refraction!of!Light!Laboratory! ! Page!1!of!4!

Laboratory+Experiment+Use!a!pencil!and!ruler!to!draw!the!following!on!the!empty!page!included.!

Conduct!the!experiment!

1. Position!the!ray!box!outside!the!measuring!circle!of!the!provided!page.!The!ray!box!should!be!located!on!one!side!of!the!solid!line!drawn!in!the!centre!of!the!page.!The!light!projected!from!the!ray!box!should!pass!through!the!required!angle!as!well!as!the!indicated!point!in!the!centre!of! the! page! (indicated! by! a! dashed! line! representing! a! normal! that! intersects! a! solid! line!representing!where!two!mediums!meet).!

2. Place!the!glass!slab!on!the!page!provided!so!that!the!clear!surface!is!aligned!with!the!solid!line!in!the!centre!of!the!page.!The!side!with!clear!tape!should!be!on!the!side!furthest!from!this!line.!

3. On!the!page,!mark!the!point!in!which!the!beam!of!light!is!seen!exiting!the!side!of!the!glass!slab!with!the!clear!tape.!

4. Remove!the!glass!slab!and!the!ray!box.!

Make!a!ray!diagram!

1. Draw!an!incident!ray!by!making!a!line!from!the!angle!indicated!on!the!page!with!point!where!the!beam!of!light!met!the!medium!and!the!indicated!normal.!

2. Draw!a!refracted!ray!by!making!a!line!from!the!point!where!light!entered!the!glass!slab!to!the!marked!point!on!the!page.!Extend!this!line!so!it!passes!outside!the!measuring!circle.!

Measure,!record,!share,!and!calculate!!

1. Measure! and! record! the! incident! angle! and! the! angle! of! refraction! in! the! table! provided!(Results! and! Observations! on! the! next! page).! Share! the! results! with! your! group! partners! to!complete!results!for!each!of!the!indicated!angles.!

2. Each! groupQmember! completes! one! of! the! required! angles! indicated! in! the! table! and! shares!with!the!other!members!of!the!group.!

3. Complete!the!required!calculations!also!noted!in!the!table.!

! !


!

Name!!


Use!this!page,!with!the!measuring!circle!below,!to!conduct!the!laboratory.!!

! !


!

Name!!


Results+and+Observations+

∠!!" ∠R" ∠!∠!" sin∠!!" sin∠R" sin∠!

sin∠!"

30°" " " " " "

40°" " " " " "

50°" " " " " "

60°" " " " " "

Note:!When!using!the!trigonometric!functions!of!your!calculator,!make!sure!you!are!in!the!“degrees”!(deg)!mode.!!From! the! calculations!made! from!your! results! and!observations! (see! table! above),!what! conclusions!can!you!make?!

What!is!the!mathematical!relationship!between!the!incident!and!reflective!rays!to!the!speed!of!light!in!a!medium?!! !


!

Name!!


Application+Questions+Solve!the!following!problems.!

1. The!speed!of! light! in! salt! (sodium!chloride)! is!1.96×108!m/s.!Calculate! the! index!of! refraction! for!sodium!chloride.!

2. Calculate!the!speed!of!light!as!it!is!transmitted!through!olive!oil.!

3. Light!from!air!is!observed!to!enter!a!medium!with!an!incident!angle!of!52°!and!a!refracted!angle!of!29°.!What!is!the!medium?!How!fast!does!light!travel!through!the!medium?!

SNC2D&

SNC2D&Slides&–&Refrac2on&Index&(with&Laboratory)& 1&

{"Refraction"

The&bending&or&change&in&direc2on&of&light&when&it&travels&from&one&medium&into&another.&

Refraction"

Incident&Ray&

Water&

Air&

Refracted&Ray&

The/speed/of/light/varies,/depending/on/the/medium/of/transmission."

Glass&(dense)&Air&(rare)& Air&

Speed&of&light&changes&

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Measuring/Refraction"

Incident&Ray&

Medium&2&

Medium&1&

Refracted&Ray&

normal&

angle&of&refrac2on&(�R)"

angle&of&incidence&(�i)&

1.&Incident&Ray,&Refracted&Ray,&and&normal&all&on&the&same&plane&(just&like&reflec2on).&&2.&Incident&Ray&and&Refracted&Ray&are&on&the&opposite&sides&of&the&line&indica2ng&the&separa2on&of&two&mediums.&

Conclusions"

Incident&Ray&

normal&

Refracted&Ray&

Conclusions"

Incident&Ray&

Glass&

Air&

normal&

Refracted&Ray&

�R"

�i"

Angle&of&refrac2on&less&than&incident&angle&

Light&bends&towards&the&normal&when&light&in&the&second&medium&is&slower&than&the&first&medium.&

Conclusions"

Incident&Ray& Glass&

Air&

normal&

Refracted&Ray&

�R"

�i"

Angle&of&refrac2on&greater&than&incident&angle&

Light&bends&away*from&the&normal&when&light&in&the&second&medium&is&faster&than&the&first&medium.&

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Lab/demonstration"Lab:/Measurements/for/calculation"

Medium&–&Glass&

Medium&–&Air&

normal&

�R"

�i"

�i!" �R" �i!"�R" sin�i" sin�R" sin�i"

sin�R"

30°"

40°"

50°"

60°"

Observations/and/Results"

�i!" �R" �i!"�R" sin�i" sin�R" sin�i"

sin�R"

30°" 19.0" 1.55" 0.49" 0.33" 1.51"

40°" 25.0" 1.60" 0.64" 0.42" 1.52"

50°" 30.0" 1.67" 0.77" 0.50" 1.53"

60°" 34.5" 1.74" 0.87" 0.57" 1.53"

Observations/and/Results"

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Index/of/Refraction"

sin∠isin∠R

n = =1.52


Medium" n$

Vacuum/space/and/Air" 1.00"

Ice" 1.31"

Water/(pure)" 1.33"

Ethyl/alcohol" 1.36"

QuarV" 1.46"

Vegetable/oil" 1.47"

Olive/oil" 1.48"

Acrylic" 1.49"

Glass" 1.52"

Diamond" 2.42"

What/of/the/Speed/of/Light?"

medium&

Space/vacuum&

normal&

�R"

�i"c"

v"

Speed&of&light&(vacuum)&

Speed&of&light&(medium)&

Comparing/the/Speed/of/Light"

cvglass

=3.00×108 m s1.97×108 m s

=1.52

c = 3.00×108 m s

SNC2D&



sin∠isin∠R

n = cvmedium

n =


=sin∠isin∠R

cvmedium

medium&

Space/vacuum&

normal&

�R"

�i"c"

v"

Speed&of&light&(vacuum)&

Speed&of&light&(medium)&

1.  The&speed&of&light&in&salt&(sodium&chloride)&is&1.96×108&m/s.&Calculate&the&index&of&refrac2on&for&sodium&chloride.&

2.  Calculate&the&speed&of&light&as&it&is&transmiXed&through&olive&oil.&

3.  Light&from&air&is&observed&to&enter&a&medium&with&an&incident&angle&of&52°&and&a&refracted&angle&of&29°.&What&is&the&medium?&How&fast&does&light&travel&through&the&medium?&

Questions"

SNC2D&



Medium" n$

Vacuum/space/and/Air" 1.00"

Ice" 1.31"

Water/(pure)" 1.33"

Ethyl/alcohol" 1.36"

QuarV" 1.46"

Vegetable/oil" 1.47"

Olive/oil" 1.48"

Acrylic" 1.49"

Glass" 1.52"

Diamond" 2.42"

snc2d – refraction index lesson plan - weebly...snc2d snc2d lesson plan refraction index (with...

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