Kean University Continuing Education

Implementing the Science Standards K-4


Sun and Shadows

Introduction

A sunny day can be a bright and cheery experience. Students can learn about the position of the Sun in the sky by learning the properties of shadows.

Students can also learn about how the Sun moves in the sky by observing shadows.

The above motions of your shadow occur in the Northern Hemisphere because the Sun travels from the east, through the south and to the west in the Northern Hemisphere. These are also the motions that you would see using a sundial. The mechanical clock was developed in the middle ages in Europe. The hands on the clock move in the clockwise direction which is the same direction your shadow moves during the day if you are facing north.

An important note about observing the Sun

The Sun should never be observed directly with the eyes and especially not with a telescope or binoculars. There is a great risk of permanent eye damage which can happen instantaneously especially with telescopes. Using household items such as stacks of camera film will not work because, although they filter out some of the visible light, the invisible rays that do the damage are not filtered out.

There are several safe ways to view the Sun indirectly which are safe to use. The pinhole projector and the mirror projector can be used safely as long as they are not aimed directly into someone's eyes.

Activity. Pinhole solar projector

Introduction

The pinhole solar projector can be used to cast an image of the Sun onto a white card. This is done with the back toward the Sun. The sunlight passes over the shoulder and onto the cards so that the observer is looking away from the Sun at all times.

Materials

Procedure

1. Students discuss the importance of not looking into the Sun at any time. They write in their Science Journals about eye damage caused by looking into the Sun, even for an instant.

2. Students discuss the path of light using the pinhole solar projector. They predict what the appearance of the Sun will be when it is projected onto the solid index card.

3. Students use the pin to make a small hole in one of the index cards. They hold the index card in front of them with the sunlight coming in over their shoulder. The other index card is held in the shadow of the first card. An image of the Sun will appear on the second card.

Results

1. Students observe the Sun as projected on the index card. They describe the appearance of the Sun on the card by writing in their Science Journals.

2. Students experiment with larger holes and moving the second card toward or away from the first card to see which positions give the sharpest image of the Sun.

Activity: Mirror solar projector

Introduction

A small flat mirror can be covered with a card that has a hole punched in it. This will permit the Sun to reflect off the mirror but only in the area that is left uncovered. If the mirror is placed on a sunny window sill, a reflection of the Sun will appear on the ceiling or wall, depending upon the way the mirror is placed.

Materials

Procedure

1. Students discuss the importance of not looking into the Sun at any time. They write in their Science Journals about eye damage caused by looking into the Sun, even for an instant. This includes when the Sun is reflected off a mirror.

2. Students discuss how to place the card on the mirror to project the Sun. They predict what will happen when the mirror is covered with the card and placed in the sunlight. They record their predictions in their Science Journals.

3. Students make the device and place it in the sunlight. The record their observations in their Science Journals.

Results

1. Students have made a series of observations of the reflection of the Sun. These are written in their Science Journals.

2. Students move the mirror around to see if there is any change in the reflected Sun that they see in the room. They are careful to make sure that the Sun never shines into anyone's eyes.

3. Students leave the mirror in one place and watch the reflection of the Sun for a long period of time. If they can reflect the Sun onto the bulletin board, they can mark the edge of the Sun with tacks every five or 10 minutes to demonstrate that the reflection of the Sun moves across the board because the Sun is changing its position in the sky constantly.

Activity: Shadows

Introduction

Any bright light will cast a shadow. This is true of a flashlight when you use it in a dark room, it is true of the Moon on a clear night with a bright Moon, and it is true of the Sun. The Sun has the brightest light so it casts the most distinct shadows.

Materials

Procedure

1. Students discuss the objects that they will work with in this investigation. They make predictions about what will happen when they shine the flashlight on them. They write the predictions in their Science Journals.

2. They shine the flashlight on the various objects. In their Science Journals they record the shape of the shadow and the location of the shadow in relation to the location of the flashlight.

3. They hold the object still in one place and move the flashlight to different locations so that it continuously shines on the object. They record what happens with the shadow when they move the flashlight.

Results

1. Students have recorded the shape of the shadow for each of the objects. They will note that the shadow is the same shape as the object.

2. When the flashlight was moved the shadow also moved. The shadow moves in such a way to stay directly opposite the location of the flashlight.

Activity: Daytime and Shadows

Introduction

The students now apply their knowledge of the properties of shadows to the shadows that are seen outdoors on a sunny day. This activity can also be done indoors as the shadows will have the same properties whether the objects are indoors or outdoors. It is a good idea to remind the students never to look directly into the Sun, even for an instant.

Materials

Procedure

1. Students begin by discussing what the results were when they studied shadows made by a flashlight. They predict what the properties of shadows will be when the Sun is used as the light source.

2. Without looking into the Sun, students observe objects illuminated by the Sun. They make a list of the objects in their Science Journals and describe the properties of the objects and the shadows the objects cast.

Results

1. Students have a list in their Science Journals of objects that were illuminated by the Sun and the properties of the shadows.

2. Students determine if the relationships of the objects to the shadows that they had with the flashlights holds true when the Sun is illuminating objects.

3. In the classroom, they can also use the same objects that they used with the flashlights and see the properties that the shadows have when the Sun is used to illuminate them.

Activity: How Shadows Move

Introduction

Students learn that the Sun rises in the east, travels across the southern part of the sky and sets in the west. From their knowledge of the properties of shadows they predict how the shadow of a single object will behave during the day.

Materials

Procedure

1. Students review and discuss what they have learned about the properties of shadows.

2. Students observe the shadow cast by an object in a fixed location outdoors. A fence post or other vertical object is ideal. It would be best if they could observe the object on a day when it is clear all day. It is also desirable to have several observations, one in the morning, one at noontime and one in the afternoon.

3. Students record the position of the shadow at various times during the day in their Science Journals. An example is shown in the figure.

Results

1. Students have observed the motion of the shadow of the vertical object and have made notes and drawings about it in their Science Journals. They can use chalk or sticks and mark on the ground the location of the shadow in the morning, at noontime and in the afternoon.

2. Students write in their Science Journals about the direction the shadow moves during the day. The drawing in the figure illustrates the position of the post and the shadow when viewed from the south. This means that the observer is looking north when the drawings are made.

3. Students note that the path taken by the shadow is the same as the path taken by the hour hand on the clock.

Discussion

1. Students use small sticks and mark the position of the post every hour. They leave the sticks in place and return the next day to see if the Sun shines in the same location at the same time during the day.