{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

# HW3 - PHYS 4D Solution to HW 3 Problem Giancoli 31-34(II...

This preview shows pages 1–2. Sign up to view the full content.

PHYS 4D Solution to HW 3 January 20, 2011 Problem Giancoli 31-34 (II) Estimate the radiation pressure due to a 75-W bulb at a distance of 8 . 0 cm from the center of the bulb. Estimate the force exerted on your fingertip if you place it at this point. Solution: Using Eq. 31-21a, P = S c = P 4 πd 2 c = 75 W 4 π (8 . 0 × 10 - 2 m ) 2 3 . 00 × 10 8 m/s = 3 . 1 × 10 - 6 N/m 2 . The force is pressure times area. We approximate the area of a fingertip to be 1 . 0 cm 2 , F = PA = ( 3 . 1 × 10 - 6 N/m 2 ) ( 1 . 0 × 10 - 4 m 2 ) = 3 . 1 × 10 - 10 N. Problem Giancoli 31-35 (II) Laser light can be focused (at best) to a spot with a radius r equal to its wavelength λ . Suppose that a 1 . 0- W beam of green laser light ( λ = 5 × 10 - 7 m ) is used to form such a spot and that a cylindrical particle of about that size (let the radius and height equal r ) is illuminated by the laser as shown in Fig. 31-23. Estimate the acceleration of the particle, if its density equals that of water and it absorbs the radiation. [This order-of-magnitude calculation convinced researchers of the feasibility of ”optical tweezers,” p. 829.] Solution: SA = dU dt = 1 . 0 W.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern