Rdio waves

[izzieamy]

Radio waves travel at the speed of light (300 000 000. m/s)
Radio 3 has a frequency of 90 MHz

a) write down the frequency in Hz in standard form ????

HELP PLEASE

thank you

x

[north star]

Standard form, I think is written as eg 2.7 x 10 to the power of something.(sorry don't know how to do superscript)

90 MHz is 90 Mega Hz.

Mega is 10 to the power of 6.

so your answer is.......

[izzieamy]

north star i dont understand .... i mnot the brightest button in the box ...... but is the answer therefore

10 to the power of 6 ???

[north star]

I think the question is asking you to express 90 MHz in a form similar to this.....

http://en.wikipedia.org/wiki/Scientific_notati on

[heathfield]

The radio wave is travelling at approximately the speed of light as you say. But it is effectively reversing its polarity at a frequency of 90 million times a second, i.e. 90MHz. (M = Mega = million, Hz = Hertz = cycles), so you could write this as 90,000,000 Hz. If you were receiving the BBC on long wave at 200KHz, the radio wave is still travelling at near light speed, but is reversing its polarity at only 200 thousand times a second. (K = Kilo = 1000, Hz = Hertz = cycles). Thus 200,000 Hz. Hope this helps.

[R1Geezer]

The speed of radio/light is uirrelevant to this simple notational excercise

90Mhz = 90,000,000Hz = 0.9x10**8 Hz (** = to the power of, ie 10 x 10 x 10 x 10 x 10 x 10 x 10 x 10

"standard form" is written as a number between -1 and +1 mutiplied by 10 to the power of whatever it takes to make the number. eg the number 5 in standard form is
0.5 x 10**1

[heathfield]

Some confusion here...

There's standard notation for numbers, where these are shown in full, such as 90,000,000

Then there's standard form for scientific notation. I'm not sure where R1Geezer gets his -1 and +1 from, since in the standard form for scientific notation a number is written with a single digit before the decimal point equal to or not less than 1, and, (obviously), less than 10.

Further explanation can be found here.

[R1Geezer]

sorry heathfield bit rusty you are correct standard form has one digit before the decimal point.

I was thinking of Floating point that is used in Computing, a floating point number is represented thus

-/+ME-/+XX

M=mantissa -1 -> +1 , XX eXponent + or - anything

eg 258 would be +0.258E03

[north star]

Heathfield & R1geezer, I will point out that the OP has not returned to this thread, spare a minute and give some thought as to why that might be.

[heathfield]

My original thought was that Izzie should have paid more attention in the maths class. ;0)