Physics in Light- Intensity

Investigations in Light Intensity Change through angular Displacement Guiding Question How does the persuasiveness of light change as the lean of incidence to the light source augments? Prediction of Results Predict what you conceptualize entrust happen and what type of equation and graph might scoop fit the data representing the strength of a light as the tend of incidence increases. Objective After completing this lesson, a student should be able to analyze light intensity striking a issue at vary angles of incidence.Materials CBL, TI-83 Plus calculator, light sensor, lamp with light bulb (60 to nose tindy watts), tape measure, Scotch tape (or similar), protractor, sheet of paper, ANGLE program, daily log Vocabulary the normal angle of incidence periodic sinusoidal reversion Introduction You have completed an investigation of light intensity changes with varying distance. You will continue investigating intensity changes, but now you will note the change of intensit y as light strikes a excavate through increase angles of incidence.As Figure 1 indicates, the angle of incidence is the angle at which light strikes a surface. The normal is an imaginary line erect to the plane on which light strikes. The angle of incidence is the angle surrounded by the normal and an consequent (that is, an incoming) light ray. Angle of incidence Normal incidental Light Ray Figure 1 As the angle of incident light increases, is it more reasonable to think that its intensity increases or decreases? As you think about this question, consider whether you are more likely to build up a sunburn in the late level when the sun is imprint on the horizon greater incidence angle) or at midday time when the sun is more oerhead (smaller incidence angle), as sketched on a lower floor? Is it usually hotter at noon or in the late evening? Evening Sunlight twelve noon Sunlight If you suspect that intensity decreases with increasing angle of incidence, you are on the right t rack. Assuming for the moment, accordingly, that the light intensity (I) decreases as the angle of incidence (a) increases, we can say the relationship in the midst of intensity and incidence angle are backwardly proportional over the angles involved.But you may note that as the sun rises through the morning and then sets toward the evening, its angle of incidence decreases, reaches a minimum at noon, and then begins to increase again into the evening. That is, the incidence angle starts at sunrise at a maximum of 90, decreases to a minimum until noon (near the equator it decreases to 0, but not in Alaska), and then increases back to a maximum to 90 at sunset.You can see that this cycle repeats itself time and again the incidence angle begins at a maximum, then decreases to a minimum, increases to a maximum, and so forth. Figure 2a below shows just such a cycle. Intensity, however, changes as the inverse of the incidence angle, so is represented in the Figure 2b cycle. Morning n oontide Evening Figure 2a Changing Incidence Angle Morning Noon Evening Figure 2b Changing Light Intensity This cycle of repeating events is called periodic and you might recognize the curves as sinning waves.Here is an equation that describes intensity as a sine wave I = sin(a) (intensity is proportional to the sine of the incidence angle, a). It is important to remember in this comparison that the angle with jimmy to the sun will always be between 90 and 0. This means that if we determine one quarter of the period (or cycle), then we can know through regression analysis what the rest of the curve should envision like. You will complete an investigation that does exactly this determine the intensity of a light as the angle of incidence changes from 0 to 90.