Math Is Fun Forum

mathxyz

Member

From: Brooklyn, NY

Registered: 2024-02-24

Posts: 1,053

Wavelength of Visible Light

The wavelength of visible light is about 5 x 10^(-7) meter. Express this wavelength as a decimal.

I guess the question wants me to convert from scientific notation to decimal form.

Now 10^(-7) means to move 7 places to the right of 5.

Yes?

In that case, 5 x 10^(-7) becomes 5,000,000.

You say?

Bob

Administrator

Registered: 2010-06-20

Posts: 10,627

Re: Wavelength of Visible Light

No. Move to the left to make a very small number.

B

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

mathxyz

Member

From: Brooklyn, NY

Registered: 2024-02-24

Posts: 1,053

Re: Wavelength of Visible Light

No. Move to the left to make a very small number.

B

I thought that a negative power means to move to the right.

Are you saying that the answer is 0.000,000,5?

Last edited by mathxyz (2024-05-11 08:33:11)

Bob

Administrator

Registered: 2010-06-20

Posts: 10,627

Re: Wavelength of Visible Light

Yes.

The negative powers make the actual number small.  Positive powers make the number big.

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

mathxyz

Member

From: Brooklyn, NY

Registered: 2024-02-24

Posts: 1,053

Re: Wavelength of Visible Light

Yes.

The negative powers make the actual number small.  Positive powers make the number big.

Bob

Can you show me the actual scientific notation rule for this in a general formula?

Bob

Administrator

Registered: 2010-06-20

Posts: 10,627

Re: Wavelength of Visible Light

The notation was invented to make it easier to write very big or very small numbers.

eg 12 000 000 000 000 becomes 1.2 x 10^(13)

0.0000000000000000012 beocmes 1.2 x 10^(-18)

The rule is (a number between 1 and 10) x (the right power of ten so the value of the number is preserved)

Positive powers of ten make numbers bigger and negative numbers smaller.

eg.

12340000

Put the point between the 1 and 2, then count how far it has 'moved' and correct for this by having the right power of ten.

1.234 x 10^(7)

eg.

0.00001234 becomes

1.234 x 10^(-5)

Scientific calculators automatically jump into standard form when the value won't 'fit' the display space.

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

mathxyz

Member

From: Brooklyn, NY

Registered: 2024-02-24

Posts: 1,053

Re: Wavelength of Visible Light

The notation was invented to make it easier to write very big or very small numbers.

eg 12 000 000 000 000 becomes 1.2 x 10^(13)

0.0000000000000000012 beocmes 1.2 x 10^(-18)

The rule is (a number between 1 and 10) x (the right power of ten so the value of the number is preserved)

Positive powers of ten make numbers bigger and negative numbers smaller.

eg.

12340000

Put the point between the 1 and 2, then count how far it has 'moved' and correct for this by having the right power of ten.

1.234 x 10^(7)

eg.

0.00001234 becomes

1.234 x 10^(-5)

Scientific calculators automatically jump into standard form when the value won't 'fit' the display space.

Bob

Very good notes. This is a good skill to know. I used to work at the AMNH. When on patrol, I recall reading about planets in Section 18 which is all about astronomy and also where the famous planetarium is located. All numbers on the boards with information for visitors to read about distances between planets are in scientific notation.