Planck’s Constant Apparatus

Product Description

Functions as a ready-built circuit for the classic measurement of Planck’s constant using the photoelectric effect. Ideal for use in conjunction with the Edu-Lab Picoammeter (614-008). Within the unit are a caesium antimony cathode (spectral response range: 185-650nm), a D/C power supply with a potentiometer to provide a variable retarding voltage to the photoelectric circuit and a digital display showing the retarding voltage, needed to reduce the current to zero (adjusted via the potentiometer). 6 Different coloured lenses are provided to vary the value of ¡®f¡¯ and a 4mm to UHF lead is included for connecting the picoammeter to the apparatus. (When using with the Edu-Lab Picoammeter, a UHF to UHF lead is required – please request this alternative lead when ordering). When light of frequency ¡®f ¡® strikes the cathode, electrons of energy ¡®E= hf-W0¡¯ are released to produce a tiny current, which is registered by the picoammeter. The potentiometer is adjusted to determine the value of ¡®V¡¯ at which the current reaches zero. By measuring ¡®V¡¯ at different frequencies of light (via filters), then plotting ¡®V¡¯ against ¡®F¡¯, the gradient can be estimated and used to approximate ¡®h/e¡¯. Specification: ? Dimensions: 205 x 150 x 115mm (W x H x D) ? DC Stopping potential controlled by 10-turn potentiometer ? DC voltmeter with 0-19.99V LED display ? Filters: 6 narrow-band (FWHM bandwidth: 4-15nm), with wavelengths of 405nm, 450nm, 510nm, 550nm, 590nm and 630nm ? Female UHF socket for connection to picoammeter ? Included input lead: UHF male to 2 x 4mm plugs (unless UHF to UHF is requested) ? Photocell: caesium antimony cathode, spectral response range: 185-650nm ? Power source: 9V PP3 battery