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Rings of Glass in a Lighthouse

4th grade nonfiction passage about lighthouse lenses: 231 words, six questions, an answer key and vocabulary.

4th grade nonfiction lighthouse lenses 231 words

Rings of Glass in a Lighthouse

A lighthouse has a big job. It must send a bright beam of light far across the sea, so that ships can see it from a long way off. A lamp alone is not enough. A lamp sends light in all directions, and most of it would be wasted. A lens can gather that light and bend it into one strong beam.

The trouble is that a lens big enough to do the job would be very thick and very heavy. Glass that thick would be hard to make and hard to carry up a tall tower. About two hundred years ago, a French scientist named Augustin Fresnel found a better way. He built a lens out of many rings of glass. Each ring was thin, and each was cut at just the right angle to bend the light forward. Together they worked like a huge lens, but they weighed far less.

The lamp sat in the middle of the rings. In many lighthouses, the whole lens slowly turned, so the beam swept across the water like the hand of a clock. To a sailor far away, the light seemed to flash on and off.

Each lighthouse flashes in its own pattern, with its own count of flashes and pauses. A sailor who learns the pattern can tell which lighthouse he is seeing, and so he knows where his ship is.

Questions

  1. Why is a lamp alone not enough for a lighthouse? in the text

  2. What is the problem with a lens that is big enough? in the text

  3. How was the new lens built? in the text

  4. Where did the lamp sit? in the text

  5. Why does the light seem to flash on and off? in the text

  6. How can a flashing pattern help a sailor find his way? think about it

Words to know

beam
a strong, narrow line of light
lens
a curved piece of glass that bends light
wasted
used in a way that does no good
angle
the shape made where two lines or surfaces meet
pattern
a set of things that repeats in a regular way
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One passage, three levels

The same topic and facts written three ways, so a mixed class can read and talk about one text. Each group’s sheet shows only a shape; the key says which is which.

● Easier · 176 words · Flesch-Kincaid grade 2.3

A lighthouse has a big job. It must send a bright beam far over the sea. Ships need to see it from far away. A lamp alone is not enough. A lamp sends light every way, and most is wasted. A lens can gather the light and bend it into one strong beam.

But a lens big enough would be thick and heavy. About two hundred years ago, a French scientist named Augustin Fresnel found a better way. He made a lens from many rings of glass. Each ring was thin. Each ring was cut at the right angle to bend light forward. Together they worked like a big lens, but they were much lighter.

The lamp sat in the middle of the rings. The lens slowly turned. The beam swept across the water like the hand of a clock. A faraway sailor saw the light flash on and off.

Each lighthouse has its own pattern of flashes. A sailor learns the pattern and knows which lighthouse it is. Then he knows where his ship is.

▲ This passage · 231 words · Flesch-Kincaid grade 4.1

A lighthouse has a big job. It must send a bright beam of light far across the sea, so that ships can see it from a long way off. A lamp alone is not enough. A lamp sends light in all directions, and most of it would be wasted. A lens can gather that light and bend it into one strong beam.

The trouble is that a lens big enough to do the job would be very thick and very heavy. Glass that thick would be hard to make and hard to carry up a tall tower. About two hundred years ago, a French scientist named Augustin Fresnel found a better way. He built a lens out of many rings of glass. Each ring was thin, and each was cut at just the right angle to bend the light forward. Together they worked like a huge lens, but they weighed far less.

The lamp sat in the middle of the rings. In many lighthouses, the whole lens slowly turned, so the beam swept across the water like the hand of a clock. To a sailor far away, the light seemed to flash on and off.

Each lighthouse flashes in its own pattern, with its own count of flashes and pauses. A sailor who learns the pattern can tell which lighthouse he is seeing, and so he knows where his ship is.

■ Harder · 241 words · Flesch-Kincaid grade 6.5

A lighthouse has an important job to do. It must send a bright beam of light far across the sea, so that ships can see it from a great distance. A lamp alone is not sufficient, because a lamp sends light in every direction and most of it would be wasted. A lens, however, can gather that light and bend it into a single, powerful beam.

The difficulty is that a lens large enough to do the job would be extremely thick and heavy. Glass of that size would be hard to make and even harder to carry up a tall tower. About two hundred years ago, a French scientist named Augustin Fresnel discovered a much better approach. He constructed a lens out of many rings of glass. Each ring was thin, and each was cut at precisely the right angle to bend the light forward. Together they performed like an enormous lens, yet they weighed far less.

The lamp sat in the center of the rings. In many lighthouses, the whole lens turned slowly, so that the beam swept across the water like the hand of a clock. To a sailor far away, the light appeared to flash on and off.

Every lighthouse flashes in its own pattern, with its own count of flashes and pauses. A sailor who learns the pattern can identify which lighthouse he is looking at, and therefore he can work out where his ship is.

Download as one PDF

How to use it

  1. Press Read it big (or B) to put the text on the projector, or Full screen (F) to fill the whole screen.
  2. Ask the questions one at a time and use Show answer when the class has decided. A shows or hides every answer.
  3. Print student copy for the class, or Print with answers for yourself.

Ideas for class

  • Before reading, put beam, lens, wasted, angle and pattern on the board with their meanings from the Words to know section and have students predict what the text will be about.
  • Read it aloud once while students follow along, then have them reread it alone or with a partner. At a calm 100 words a minute it takes about 2 minutes to read aloud.
  • Use the Read it big button (or B) to put the text on the projector, and Show answer on one question at a time so the class commits to an answer first.
  • Question 6 asks the reader to infer. Ask students to point to the words in the passage that led them to their answer.
  • Ask students to write one question the passage did not answer, then look for the answer in a book or on a classroom screen.
  • Print the student copy for independent work and keep the answer-key copy for yourself.

Related

Questions

What reading level is "Rings of Glass in a Lighthouse"?

It was written for 4th grade. It has 231 words and works out to a Flesch-Kincaid grade level of about 4.1. That is a formula's estimate from sentence length and syllables, and it is not a Lexile or a guided reading level, so check it against your students.

What do the questions ask?

There are six. 5 ask for something the text says directly and 1 ask the reader to work something out from clues. Each has an answer in the key, and the answers are written as a teacher would accept them, not as the only possible wording.

How long does it take to read?

About 2 minutes read aloud at 100 words a minute. For a one-minute fluency check, paste it into the fluency timer and use the word count.

Can I print it?

Yes. Print student copy gives the passage, the questions with lines to write on, and the word meanings. Print with answers gives the same page with the answers filled in. Both are made in your browser.

Is this passage from a published book?

No. It was written for Peabody Teach, so there is no book to buy and no login to read it.

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