1. Announcements 2/24/12 Prayer I’ll be out of town Monday and Wednesday of next week. Dr. Peatross will be substitute. Curtis, are you here? Please come talk to me briefly. (Message from Dr Asplund.)

2. Reading Quiz Which of the following is the correct expression for the delta function shown (infinitely high, infinitely narrow)? a. a.  (x) b. b.  (x+x 0 ) c. c.  (x-x 0 ) d. d.  (x  x 0 ) e. e.  (x/x 0 )

3. Reading Quiz Which of the following is known as the “sifting property” of the delta function? a. a. d. b. b. e. c. c.

4. Delta function basics (from handout) Definition(s) “Sifting” property Fourier transform(s)

5. Comb function FT of comb with 21 peaks, without a 1/sqrt(2  ) factor 2  /21 21, or really 21/sqrt(2  )

6. Reading Quiz What symbol did I use for the convolution in my convolution handout? a. a.+ b. b.  c. c.  d. d.  e. e. 

7. Reading Quiz Aside from a constant factor, the Fourier transform of a convolution of two functions is the product of their Fourier transforms. a. a.true b. b.false FT(f  g) = FT(f)  FT(g)

8. Reading Quiz Aside from a constant factor, the Fourier transform of a product of two functions is the convolution of their Fourier transforms. a. a.true b. b.false FT(f  g) = FT(f)  FT(g)

9. Convolution basics, from handout Context Definition

10. Class survey (ungraded) Did you go to the recommended website applet? http://www.jhu.edu/~signals/convolve/index.html http://www.jhu.edu/~signals/convolve/index.html a. a.yes b. b.no

11. Class survey (ungraded) Will you go to the recommended website applet? http://www.jhu.edu/~signals/convolve/index.html http://www.jhu.edu/~signals/convolve/index.html a. a.yes b. b.no

12. “Convolution theorems” FT(f  g) = FT(f)  FT(g) FT(f  g) = FT(f)  FT(g) (and application to time-resolved spectroscopy)