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Students will study how lenses and mirrors form images.
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Students will observe and discuss mirror images of various objects .
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Students will list and describe as many optical instruments that use lenses.
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Students will form images using convex lens.
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As previously mentioned light travels in a straight line. However, when light moves from one medium to another, the direction of the light changes. When a beam of light passes from air into glass, the path of light will be bent or refracted. The glass is the transparent material used in most lenses that refracts light. There are two main types of lenses:- a) Convex lenses b) Concave lenses. Light passing through a convex lens is bent inwards whereas light passing through a concave lens is bent away from the lens. Within a convex lens the light rays are brought together at a focal point. As the light leaves the lens, it is also refracted. The amount of refraction depends on the curvature of the lens. The lens in our eyes is an example of a convex lens which projects a real image on to the retina of the eye upside down.
OBJECTIVES
Students will be able to :
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explain what causes solar and lunar eclipses
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recognize and identify the different phases of the moon
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determine the sequence of lunar phases
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Our planet's satellite, which we call the moon continues to remain an object of fascination and inquiry for astronomers and other scientists who study not only its motion but materials such as rocks brought back from its surface. The moon is the easiest astronomical object to observe with the naked eye. For many students, the moon appears to them in many different forms related to its changing appearance. They sometimes ask, " Why does the moon appear to change shape?" The moon appears to change shape because of the way it reflects light from the sun. The changing shapes of the moon are called phases. The phases of the moon depend upon the positions of the sun, the moon and the earth.
The moon's orbit around the earth once in about twenty-eight days changes what part of the moon is lighted by the sun and how much of that part can be seen from the earth. We all see the moon because sunlight reflects back to us from its surface. During the course of the month, the moon circles once around the earth. That portion of the moon facing the sun is always lit; however, this lit-up side does not always face the earth. As the moon circles the earth, the amount of its disk facing us that is lit by the sun changes, altering how much of the lunar surface appears bright and how much is in darkness. These changes, called phases repeat in a specific cycle each month. These phase range from new to waxing crescent, first quarter , waxing gibbous and full, then reversing to waning gibbous, last quarter, waning crescent and new to begin the cycle again. The focus of this section will be on the four primary phases: New moon, First Quarter, Full Moon and Last quarter.
Since ancient time, it has been known that the phases change as the angle made by lines from the Sun to the Moon to the Earth changes. As this angle changes, the fraction of the moon's illuminated side visible from earth changes. This phase changes as the angle between the Sun, Moon and Earth changes. For example, when the moon is on the opposite side of the Earth from the Sun, we see all of its illuminated surface and call it "full moon". As the moon revolves around the earth, a small part of it becomes visible. When the moon is in approximately the same direction as the sun with its dark side facing us, this is referred to as a "new moon". As the moon revolves around the earth, its visible portion increases and it is known to be waxing. The first phase is called the waxing crescent phase. Less than half of the moon is visible at this phase. When the moon has moved one-quarter of the way around the earth, it enters the first-quarter phase. At this phase one half of the side of the moon facing the earth is visible. As the moon continues in its orbit more and more of the side facing the earth becomes visible. This is called the waxing gibbous phase. More than half of the moon is visible during this phase. Finally, the moon completes half of its trip around the earth. The whole surface of the moon facing the earth is now visible. This is called the full moon. As the moon continues to move around the earth, less and less of the surface is visible. This phase is referred to as the waning gibbous phase. The last phase of the moon is the waning crescent phase. Consequently, the moon takes approximately 29.5 days to go through all of its phases.
ENGAGEMENT
Students will be encouraged to demonstrate these phases thus uncover any misconceptions they may have about how the moon's appearance changes.
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students will observe, describe and sequence "lunar phase photos".
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this activity will be extended to observing the moon in the night sky over a period of time to really see how the moon's appearance actually changes.
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students will make a daily , visual record of moon observations and try to make predictions of the moon's phases.
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students will create a "lunar calendar" identifying each of the moon's phases.
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