Scale: the info bar (read by OCR) says "[lab] SEI 5.0kV X5,000 WD10.0mm" and shows a 1 um scale bar. The bar is 53 px long (columns 1202-1254), so 1000 nm / 53 px = 18.9 nm per pixel. The TIFF metadata has no usable calibration (72 dpi only). At X5,000 the 1280 px width is about 24 um.

Method: I cropped the SEM area (rows 0-949, excluding the info bar), removed the background with a Gaussian high-pass, applied a Hann window and took a zero-padded 2D FFT. The dominant peak is at spatial frequency kx = +/-27 cycles per image width, ky about 0, which is a period of 47.1 px (the peak spans roughly 45-49 px).

Result: 47.1 px x 18.9 nm/px = about 890 nm (uncertainty roughly +/-5%, from the scale bar length and peak width).

Orientation: the wave vector is along the horizontal image axis (angle about 0 deg to the x axis). The periodic structures are therefore vertical stripes or ripples, running along the image y axis (top to bottom) and repeating left to right.

RESULT: period = 890 nm
